Change search
Refine search result
1234567 1 - 50 of 859
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Toneli, D. A.
    et al.
    Univ Fed Sao Paulo, Dept Sci & Technol, BR-12231280 Sao Jose Dos Campos, Brazil..
    Pessoa, R. S.
    Technol Inst Aeronaut, Dept Phys, BR-12228900 Sao Jose Dos Campos, Brazil..
    Roberto, M.
    Technol Inst Aeronaut, Dept Phys, BR-12228900 Sao Jose Dos Campos, Brazil..
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland.
    A global model study of low pressure high density CF4 discharge2019In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 28, no 2, article id 025007Article in journal (Refereed)
    Abstract [en]

    We present a revised reaction set for low pressure high density CF4 plasma modelling. A global model (volume averaged) was developed to study a CF4 discharge that includes the neutral species CF4, CF3, CF2, CF, F-2, F, and C, the metastable states CF(a(4)Sigma(-) ) and CF2(B-3(1)), the positive ions CF3+, CF2+, CF+, CF2+, F+ and C+, the negative ions CF3-, F-2(-), and F- and electrons. The main reactions that contribute to the production and loss of each species are pointed out with an emphasis on the radicals CF2, CF and F, the dominant positive ion CF3+, and the dominant negative ion F-. We find wall processes to have a significant influence on the discharge. The density of F-2 is high due to recombination of F atoms at the walls and the losses of the radicals F, CF, and CF3 are mainly through wall recombination. As the pressure is increased, F- becomes the dominant negative charged species. The discharge is found to be weakly electronegative below similar to 10 mTorr and the electronegativity decreases with increased absorbed power.

  • 2.
    Ström, Petter
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Bergsåker, Henric
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tholerus, Simon
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Rachlew, Elisabeth
    KTH, Superseded Departments (pre-2005), Physics. KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Vallejos, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Johnson, T.
    Stefanikova, E.
    Zhou, Y.
    Zychor, I.
    et al.,
    Analysis of deposited layers with deuterium and impurity elements on samples from the divertor of JET with ITER-like wall2019In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 516, p. 202-213Article in journal (Refereed)
    Abstract [en]

    Inconel-600 blocks and stainless steel covers for quartz microbalance crystals from remote corners in the JET-ILW divertor were studied with time-of-flight elastic recoil detection analysis and nuclear reaction analysis to obtain information about the areal densities and depth profiles of elements present in deposited material layers. Surface morphology and the composition of dust particles were examined with scanning electron microscopy and energy-dispersive X-ray spectroscopy. The analyzed components were present in JET during three ITER-like wall campaigns between 2010 and 2017. Deposited layers had a stratified structure, primarily made up of beryllium, carbon and oxygen with varying atomic fractions of deuterium, up to more than 20%. The range of carbon transport from the ribs of the divertor carrier was limited to a few centimeters, and carbon/deuterium co-deposition was indicated on the Inconel blocks. High atomic fractions of deuterium were also found in almost carbon-free layers on the quartz microbalance covers. Layer thicknesses up to more than 1 micrometer were indicated, but typical values were on the order of a few hundred nanometers. Chromium, iron and nickel fractions were less than or around 1% at layer surfaces while increasing close to the layer-substrate interface. The tungsten fraction depended on the proximity of the plasma strike point to the divertor corners. Particles of tungsten, molybdenum and copper with sizes less than or around 1 micrometer were found. Nitrogen, argon and neon were present after plasma edge cooling and disruption mitigation. Oxygen-18 was found on component surfaces after injection, indicating in-vessel oxidation. Compensation of elastic recoil detection data for detection efficiency and ion-induced release of deuterium during the measurement gave quantitative agreement with nuclear reaction analysis, which strengthens the validity of the results.

  • 3.
    Causa, F.
    et al.
    CNR, Ist Fis Plasma Piero Caldirola, Via R Cozzi 53, I-20125 Milan, Italy.;CNR, Ist Fis Plasma, Via R Cozzi 53, I-20125 Milan, Italy..
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Zito, P.
    ENEA, Fus & Nucl Safety Dept, CR Frascati, Via E Fermi 45, I-00044 Rome, Italy..
    Analysis of runaway electron expulsion during tokamak instabilities detected by a single-channel Cherenkov probe in FTU2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 4, article id 046013Article in journal (Refereed)
    Abstract [en]

    The expulsion of runaway electrons (REs) during different types of tokamak instabilities is analysed by means of a Cherenkov probe inserted into the scrape-off layer of the FTU tokamak. One such type of instability, the well-known tearing mode, is involved in disruptive plasma termination events, during which the risk of RE avalanche multiplication is highest. The second type, known as anomalous Doppler instability, influences RE dynamics by enhancing pitch angle scattering. Three scenarios are analysed here, characterised by different RE generation rates and mechanisms. The main conclusions are drawn from correlations between the Cherenkov probe and other diagnostics. In particular, the Cherenkov probe permits the detection of fast electron expulsion with a high level of detail, presenting peaks with 100% signal contrast during tearing mode growth and rotation, and sub-peak structures reflecting the interplay between the magnetic island formed by the tearing mode, RE diffusion during island rotation and the geometry of obstacles in the vessel. Correlations between the Cherenkov signal, hard x-ray emission and electron cyclotron emission reveal the impulsive development of the anomalous Doppler instability with instability rise time in the microsecond scale resolved by the high time-resolution of the Cherenkov probe.

  • 4.
    Keraudy, Julien
    et al.
    Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden.;Oerlikon Surface Solut AG, Oerlikon Balzers, Iramali 18, LI-9496 Balzers, Liechtenstein..
    Viloan, Rommel Paulo B.
    Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden..
    Raadu, Michael A.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Brenning, Nils
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Lundin, Daniel
    Univ Paris Saclay, Univ Paris Sud, CNRS, LPGP,UMR 8578, F-91405 Orsay, France..
    Helmersson, Ulf
    Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden..
    Bipolar HiPIMS for tailoring ion energies in thin film deposition2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 359, p. 433-437Article in journal (Refereed)
    Abstract [en]

    The effects of a positive pulse following a high-power impulse magnetron sputtering (HiPIMS) pulse are studied using energy-resolved mass spectrometry. This includes exploring the influence of a 200 mu s long positive voltage pulse (U-rev = 10-150 V) following a typical HiPIMS pulse on the ion-energy distribution function (IEDF) of the various ions. We find that a portion of the Ti+ flux is affected and gains an energy which corresponds to the acceleration over the full potential U-rev. The Ar+ IEDF on the other hand illustrates that a large fraction of the accelerated Ar+, gain energies corresponding to only a portion of U-rev. The Ti+ IEDFs are consistent with the assumption that practically all the TO-, that are accelerated during the reverse pulse, originates from a region adjacent to the target, in which the potential is uniformly increased with the applied potential U-rev while much of the Ar+ originates from a region further away from the target over which the potential drops from U-rev to a lower potential consistent with the plasma potential achieved without the application of U-rev. The deposition rate is only slightly affected and decreases with U-rev, reaching 90% at U-rev = 150 V. Both the Ti IEDF and the small deposition rate change indicate that the potential increase in the region close to the target is uniform and essentially free of electric fields, with the consequence that the motion of ions inside the region is not much influenced by the application of U-rev. In this situation, Ti will flow towards the outer boundary of the target adjacent region, with the momentum gained during the HiPIMS discharge pulse, independently of whether the positive pulse is applied or not. The metal ions that cross the boundary in the direction towards the substrate, and do this during the positive pulse, all gain an energy corresponding to the full positive applied potential U-rev.

  • 5. Tang, B. -B
    et al.
    Li, W. Y.
    Chinese Acad Sci, State Key Lab Space Weather, Natl Space Sci Ctr, Beijing, Peoples R China.;Swedish Inst Space Phys, Uppsala, Sweden..
    Graham, D. B.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Rager, A. C.
    Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA.;NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Wang, C.
    Chinese Acad Sci, State Key Lab Space Weather, Natl Space Sci Ctr, Beijing, Peoples R China.;Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Beijing, Peoples R China..
    Khotyaintsev, Yu. V.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Planetol, Toulouse, France..
    Hasegawa, H.
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Sagamihara, Kanagawa, Japan..
    Zhang, Y. -C
    Dai, L.
    Chinese Acad Sci, State Key Lab Space Weather, Natl Space Sci Ctr, Beijing, Peoples R China..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Dorelli, J. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90024 USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Crescent-Shaped Electron Distributions at the Nonreconnecting Magnetopause: Magnetospheric Multiscale Observations2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 6, p. 3024-3032Article in journal (Refereed)
    Abstract [en]

    Crescent-shaped electron distributions perpendicular to the magnetic field are an important indicator of the electron diffusion region in magnetic reconnection. They can be formed by the electron finite gyroradius effect at plasma boundaries or by demagnetized electron motion. In this study, we present Magnetospheric Multiscale mission observations of electron crescents at the flank magnetopause on 20 September 2017, where reconnection signatures are not observed. These agyrotropic electron distributions are generated by electron gyromotion at the thin electron-scale magnetic boundaries of a magnetic minimum after magnetic curvature scattering. The variation of their angular range in the perpendicular plane is in good agreement with predictions. Upper hybrid waves are observed to accompany the electron crescents at all four Magnetospheric Multiscale spacecraft as a result of the beam-plasma instability associated with these agyrotropic electron distributions. This study suggests electron crescents can be more frequently formed at the magnetopause. Plain Language Summary In this study, we present Magnetospheric Multiscale mission observations of electron crescents at the flank magnetopause and these agyrotropic electron distributions are formed at thin electron-scale magnetic boundaries after electron pitch angle scattering by the curved magnetic field. These results suggest that agyrotropic electron distributions can be more frequently formed at the magnetopause: (1) magnetic reconnection is not necessary, although electron crescents are taken as one of the observational signatures of the electron diffusion region, and (2) agyrotropic electron distributions can cover a large local time range to the flank magnetopause. In addition, upper hybrid waves accompanied with the electron crescents are observed as a result of the beam-plasma interaction associated with these agyrotropic electron distributions. This suggests that high-frequency waves play a role in electron dynamics through wave-particle interactions.

  • 6.
    Labit, B.
    et al.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Thorén, Emil
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Vallejos Olivares, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Zuin, M.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    Dependence on plasma shape and plasma fueling for small edge-localized mode regimes in TCV and ASDEX Upgrade2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 8, article id 086020Article in journal (Refereed)
    Abstract [en]

    Within the EUROfusion MST1 work package, a series of experiments has been conducted on AUG and TCV devices to disentangle the role of plasma fueling and plasma shape for the onset of small ELM regimes. On both devices, small ELM regimes with high confinement are achieved if and only if two conditions are fulfilled at the same time. Firstly, the plasma density at the separatrix must be large enough (n(e,sep)/n(G) similar to 0.3), leading to a pressure profile flattening at the separatrix, which stabilizes type-I ELMs. Secondly, the magnetic configuration has to be close to a double null (DN), leading to a reduction of the magnetic shear in the extreme vicinity of the separatrix. As a consequence, its stabilizing effect on ballooning modes is weakened.

  • 7.
    Kateb, Movaffaq
    et al.
    Univ Iceland, Inst Sci, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Univ Iceland, Inst Sci, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Ingvarsson, Snorri
    Univ Iceland, Inst Sci, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Effect of atomic ordering on the magnetic anisotropy of single crystal Ni80Fe202019In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 9, no 3, article id 035308Article in journal (Refereed)
    Abstract [en]

    We investigate the effect of atomic ordering on the magnetic anisotropy of Ni80Fe20 at.% (Py). To this end, Py films were grown epitaxially on MgO(001) using dc magnetron sputtering (dcMS) and high power impulse magnetron sputtering (HiPIMS). Aside from twin boundaries observed in the latter case, both methods present high quality single crystals with cube-on-cube epitaxial relationship as verified by the polar mapping of important crystal planes. However, X-ray diffraction results indicate higher order for the dcMS deposited film towards L1(2) Ni3Fe superlattice. This difference can be understood by the very high deposition rate of HiPIMS during each pulse which suppresses adatom mobility and ordering. We show that the dcMS deposited film presents biaxial anisotropy while HiPIMS deposition gives well defined uniaxial anisotropy. Thus, higher order achieved in the dcMS deposition behaves as predicted by magnetocrystalline anisotropy i.e. easy axis along the [111] direction that forced in the plane along the [110] direction due to shape anisotropy. The uniaxial behaviour in HiPIMS deposited film then can be explained by pair ordering or more recent localized composition non-uniformity theories. Further, we studied magnetoresistance of the films along the [100] directions using an extended van der Pauw method. We find that the electrical resistivities of the dcMS deposited film are lower than in their HiPIMS counterparts verifying the higher order in the dcMS case.

  • 8.
    Sultan, M. T.
    et al.
    Reykjavik Univ, Sch Sci & Engn, IS-101 Reykjavik, Iceland..
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Manolescu, A.
    Reykjavik Univ, Sch Sci & Engn, IS-101 Reykjavik, Iceland..
    Teodorescu, V. S.
    Natl Inst Mat Phys, Magurele 077125, Romania..
    Ciurea, M. L.
    Natl Inst Mat Phys, Magurele 077125, Romania.;Acad Romanian Scientists, Bucharest 050094, Romania..
    Svavarsson, H. G.
    Reykjavik Univ, Sch Sci & Engn, IS-101 Reykjavik, Iceland..
    Efficacy of annealing and fabrication parameters on photo-response of SiGe in TiO2 matrix2019In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 30, no 36, article id 365604Article in journal (Refereed)
    Abstract [en]

    SiGe nanoparticles dispersed in a dielectric matrix exhibit properties different from those of bulk and have shown great potential in devices for application in advanced optoelectronics. Annealing is a common fabrication step used to increase crystallinity and to form nanoparticles in such a system. A frequent downside of such annealing treatment is the formation of insulating SiO2 layer at the matrix/SiGe interface, degrading the optical properties of the structure. An annealing process that could bypass this downside would therefore be of great interest. In this work, a short-time furnace annealing of a SiGe/TiO2 system is applied to obtain SiGe nanoparticles without formation of the undesired SiO2 layer between the dielectric matrix (TiO2) and SiGe. The structures were prepared by depositing alternate layers of TiO2 and SiGe films, using direct-current magnetron sputtering technique. A wide range spectral response with a response-threshold up to similar to 1300 nm was obtained, accompanied with an increase in photo-response of more than two-orders of magnitude. Scanning electron microscopy, transmission electron microscopy, energy-dispersive x-ray spectroscopy and grazing incidence x-ray diffraction were used to analyze the morphological changes in respective structures. Photoconductive properties were studied by measuring photocurrent spectra using applied dc-voltages at various temperatures.

  • 9.
    Zhou, M.
    et al.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang 330031, Jiangxi, Peoples R China.;Nanchang Univ, Sch Environm & Chem Engn, Minist Educ, Key Lab Poyang Lake Environm & Resource Utilizat, Nanchang 330031, Jiangxi, Peoples R China..
    Huang, J.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang 330031, Jiangxi, Peoples R China.;Nanchang Univ, Sch Sci, Dept Phys, Nanchang 330031, Jiangxi, Peoples R China..
    Man, H. Y.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang 330031, Jiangxi, Peoples R China.;Nanchang Univ, Sch Sci, Dept Phys, Nanchang 330031, Jiangxi, Peoples R China..
    Deng, X. H.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang 330031, Jiangxi, Peoples R China..
    Zhong, Z. H.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang 330031, Jiangxi, Peoples R China.;Nanchang Univ, Sch Resources Environm & Chem Engn, Nanchang 330031, Jiangxi, Peoples R China..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Paterson, W. R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Royal Inst Technol, SE-75121 Stockholm, Sweden..
    Khotyaintsev, Y. , V
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    Electron-scale Vertical Current Sheets in a Bursty Bulk Flow in the Terrestrial Magnetotail2019In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 872, no 2, article id L26Article in journal (Refereed)
    Abstract [en]

    We report Magnetospheric Multiscale observations of multiple vertical current sheets (CSs) in a bursty bulk flow in the near-Earth magnetotail. Two of the CSs were fine structures of a dipolarization front (DF) at the leading edge of the flow. The other CSs were a few Earth radii tailward of the DF; that is, in the wake of the DF. Some of these vertical CSs were a few electron inertial lengths thick and were converting energy from magnetic field to plasma. The currents of the CSs in the DF wake were carried by electrons that formed flow shear layers. These electron-scale CSs were probably formed during the turbulent evolution of the bursty bulk flow and are important for energy conversion associated with fast flows.

  • 10.
    Trier, E.
    et al.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Fridström, Richard
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Vallejos, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Vignitchouk, Ladislas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Zuin, M.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    ELM-induced cold pulse propagation in ASDEX Upgrade2019In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, no 4, article id 045003Article in journal (Refereed)
    Abstract [en]

    In ASDEX Upgrade, the propagation of cold pulses induced by type-I edge localized modes (ELMs) is studied using electron cyclotron emission measurements, in a dataset of plasmas with moderate triangularity. It is found that the edge safety factor or the plasma current are the main determining parameters for the inward penetration of the T-e perturbations. With increasing plasma current the ELM penetration is more shallow in spite of the stronger ELMs. Estimates of the heat pulse diffusivity show that the corresponding transport is too large to be representative of the inter-ELM phase. Ergodization of the plasma edge during ELMs is a possible explanation for the observed properties of the cold pulse propagation, which is qualitatively consistent with non-linear magneto-hydro-dynamic simulations.

  • 11. Sultan, M. T.
    et al.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Manolescu, A.
    Stoica, T.
    Ciurea, M. L.
    Svavarsson, H. G.
    Enhanced photoconductivity of embedded SiGe nanoparticles by hydrogenation2019In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 479, p. 403-409Article in journal (Refereed)
    Abstract [en]

    We investigate the effect of room-temperature hydrogen-plasma treatment on the photoconductivity of SiGe nanoparticles sandwiched within SiO 2 layers. An increase in photocurrent intensity of more than an order magnitude is observed after the hydrogen plasma treatment. The enhancement is attributed to neutralization of dangling bonds at the nanoparticles and to passivation of nonradiative defects in the oxide matrix and at SiGe/matrix interfaces. We find that increasing the partial pressure of hydrogen to pressures where H 3 + and H 2 + were the dominant ions results in increased photocurrent.

  • 12.
    Sultan, Muhammad Taha
    et al.
    Reykjav Univ, Sch Sci & Engn, IS-101 Reykjavik, Iceland..
    Manolescu, Andrei
    Reykjav Univ, Sch Sci & Engn, IS-101 Reykjavik, Iceland..
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Torfason, Kristinn
    Reykjav Univ, Sch Sci & Engn, IS-101 Reykjavik, Iceland..
    Nemnes, George Alexandru
    Univ Bucharest, Fac Phys, MDEO Res Ctr, Magurele 077125, Romania..
    Stavarache, Ionel
    Natl Inst Mat Phys, Magurele 077125, Romania..
    Logofatu, Constantin
    Natl Inst Mat Phys, Magurele 077125, Romania..
    Teodoresu, Valentin Serban
    Natl Inst Mat Phys, Magurele 077125, Romania..
    Giurea, Magdalena Lidia
    Natl Inst Mat Phys, Magurele 077125, Romania.;Acad Romanian Scientists, Bucharest 050094, Romania..
    Svavarsson, Halldor Gudfinnur
    Reykjav Univ, Sch Sci & Engn, IS-101 Reykjavik, Iceland..
    Enhanced photoconductivity of SiGe nanocrystals in SiO2 driven by mild annealing2019In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 469, p. 870-878Article in journal (Refereed)
    Abstract [en]

    Photosensitive films based on finely dispersed semiconductor nanocrystals (NCs) in dielectric films have great potential for sensor applications. Here we report on preparation and characterization of photosensitive Si1-xGex NCs sandwiched between SiO2 matrix. A radio-frequency magnetron sputtering was applied to obtain a multilayer-structures (MLs) by depositing SiO2/SiGe/SiO2 films on Si (0 0 1) substrate. The Si1-xGex NCs were formed by a post-deposition annealing at 100-700 degrees C for 1-5 min. The effect of annealing temperature and time on MLs morphology and NCs size and density was studied using grazing incidence X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy and measurements of spectral distribution of photocurrent. It is demonstrated how the photoconductive properties of the MLs can be enhanced and tailored by controlling the NCs formation conditions and the presence of stress field in MLs and defects acting as traps and recombination centers. All these features can be adjusted/controlled by altering the annealing conditions (temperature and time). The MLs photosensitivity was increased of more than an order of magnitude by the annealing process. A mechanism, where a competition between crystallization process (NCs formation and evolution i.e. size and shapes) and stress field appearance determines the peak position in the photocurrent spectra, was identified.

  • 13.
    Fu, H. S.
    et al.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China.
    Cao, J. B.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China.
    Cao, D.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China.
    Wang, Z.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China.
    Vaivads, Andris
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Khotyaintsev, Yuri V.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA.
    Huang, S. Y.
    Wuhan Univ, Sch Elect & Informat, Wuhan, Hubei, Peoples R China.
    Evidence of Magnetic Nulls in Electron Diffusion Region2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 1, p. 48-54Article in journal (Refereed)
    Abstract [en]

    Theoretically, magnetic reconnection—the process responsible for solar flares and magnetospheric substorms—occurs at the X‐line or radial null in the electron diffusion region (EDR). However, whether this theory is correct is unknown, because the radial null (X‐line) has never been observed inside the EDR due to the lack of efficient techniques and the scarcity of EDR measurements. Here we report such evidence, using data from the recent MMS mission and the newly developed First‐Order Taylor Expansion (FOTE) Expansion technique. We investigate 12 EDR candidates at the Earth's magnetopause and find radial nulls (X‐lines) in all of them. In some events, spacecraft are only 3 km (one electron inertial length) away from the null. We reconstruct the magnetic topology of these nulls and find it agrees well with theoretical models. These nulls, as reconstructed for the first time inside the EDR by the FOTE technique, indicate that the EDR is active and the reconnection process is ongoing.

    Plain Language Summary: Magnetic reconnection is a key process responsible for many explosive phenomena in nature such as solar flares and magnetospheric substorms. Theoretically, such process occurs at the X‐line or radial null in the electron diffusion region (EDR). However, whether this theory is correct is still unknown, because the radial null (X‐line) has never been observed inside the EDR due to the lack of efficient technique and the scarcity of EDR measurements. Here we report such evidence, using data from the recent MMS mission and the newly developed FOTE technique.

  • 14.
    Torkar, K.
    et al.
    Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria..
    Nakamura, R.
    Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria..
    Wellenzohn, S.
    Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria..
    Jeszenszky, H.
    Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria..
    Torbert, R. B.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80303 USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Improved Determination of Plasma Density Based on Spacecraft Potential of the Magnetospheric Multiscale Mission Under Active Potential Control2019In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 47, no 8, p. 3636-3647Article in journal (Refereed)
    Abstract [en]

    Data from the Magnetospheric Multiscale (MMS) mission, in particular, the spacecraft potential measured with and without the ion beams of the active spacecraft potential control (ASPOC) instruments, plasma electron moments, and the electric field, have been employed for an improved determination of plasma density based on spacecraft potential. The known technique to derive plasma density from spacecraft potential sees the spacecraft behaving as a plasma probe which adopts a potential at which the ambient plasma current and one of photoelectrons produced at the surface and leaving into space are in equilibrium. Thus, the potential is a function of the plasma current, and plasma density can be determined using measurements or assumptions on plasma temperature. This method is especially useful during periods when the plasma instruments are not in operation or when spacecraft potential data have significantly higher time resolution than particle detectors. However, the applicable current-voltage characteristic of the spacecraft has to be known with high accuracy, particularly when the potential is actively controlled and shows only minor residual variations. This paper demonstrates recent refinements of the density determination coming from: 1) the reduction of artifacts in the potential data due to the geometry of the spinning spacecraft and due to effects of the ambient electric field on the potential measurements and 2) a calibration of the plasma current to the spacecraft surfaces which is only possible by comparison with the variable currents from the ion beams of ASPOC. The results are discussed, and plasma densities determined by this method are shown in comparison with measurements by the Fast Plasma Instrument (FPI) for some intervals of the MMS mission.

  • 15. Goodrich, K. A.
    et al.
    Ergun, R.
    Schwartz, S. J.
    Wilson, L. B. , I I I
    Johlander, A.
    Newman, D.
    Wilder, F. D.
    Holmes, J.
    Burch, J.
    Torbert, R.
    Khotyaintsev, Y.
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Strangeway, R.
    Gershman, D.
    Giles, B.
    Impulsively Reflected Ions: A Plausible Mechanism for Ion Acoustic Wave Growth in Collisionless Shocks2019In: Journal of Geophysical Research: Space Physics, Vol. 124, no 3, p. 1855-1865Article in journal (Refereed)
    Abstract [en]

    We present recent high time resolution observations from an oblique (43 degrees) shock crossing from the Magnetospheric Multiscale mission. Short-duration bursts between 10 and 100 ms of ion acoustic waves are observed in this event alongside a persistent reflected ion population. High time resolution (150 ms) particle measurements show strongly varying ion distributions between successive measurements, implying that they are bursty and impulsive by nature. Such signatures are consistent with ion bursts that are impulsively reflected at various points within the shock. We find that, after instability analysis using a Fried-Conte dispersion solver, the insertion of dispersive ion bursts into an already stable ion distribution can lead to wave growth in the ion acoustic mode for short durations of time. We find that impulsively reflected ions are a plausible mechanism for ion acoustic wave growth in the terrestrial bow shock and, furthermore, suggest that wave growth can lead to a small but measurable momentum exchange between the solar wind ions and the reflected population.

  • 16.
    Cozzani, Giulia
    et al.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France.;Univ Pisa, Dipartimento Fis E Fermi, I-56127 Pisa, Italy..
    Retino, A.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France..
    Califano, F.
    Univ Pisa, Dipartimento Fis E Fermi, I-56127 Pisa, Italy..
    Alexandrova, A.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France..
    Contel, O. Le
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France..
    Khotyaintsev, Y.
    Swedish Inst Space Phys, SE-75121 Uppsala, Sweden..
    Vaivads, Andris
    Swedish Inst Space Phys, SE-75121 Uppsala, Sweden..
    Fu, H. S.
    Beihang Univ, Sch Space & Environm, Beijing 100083, Peoples R China..
    Catapano, F.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France.;Univ Calabria, Dipartimento Fis, I-87036 Arcavacata Di Rende, CS, Italy..
    Breuillard, H.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France.;Univ Orleans, UMR 7328, CNRS, Lab Phys & Chim Environm & Espace, F-45071 Orleans, France..
    Ahmadi, N.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Torbert, R. B.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA..
    Nakamura, R.
    Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria..
    Fuseher, S.
    Southwest Res Inst, San Antonio, TX 78238 USA.;Univ Texas San Antonio, San Antonio, TX 78238 USA..
    Mauk, B. H.
    Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD 20723 USA..
    Moore, T.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    In situ spacecraft observations of a structured electron diffusion region during magnetopause reconnection2019In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 99, no 4, article id 043204Article in journal (Refereed)
    Abstract [en]

    The electron diffusion region (EDR) is the region where magnetic reconnection is initiated and electrons are energized. Because of experimental difficulties, the structure of the EDR is still poorly understood. A key question is whether the EDR has a homogeneous or patchy structure. Here we report Magnetospheric Multiscale (MMS) spacecraft observations providing evidence of inhomogeneous current densities and energy conversion over a few electron inertial lengths within an EDR at the terrestrial magnetopause, suggesting that the EDR can be rather structured. These inhomogenenities are revealed through multipoint measurements because the spacecraft separation is comparable to a few electron inertial lengths, allowing the entire MMS tetrahedron to be within the EDR most of the time. These observations are consistent with recent high-resolution and low-noise kinetic simulations.

  • 17.
    Lucco Castello, Federico
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Hansen, Jesper Schmidt
    Dyre, Jeppe C.
    Isomorph invariance and thermodynamics of repulsive dense bi-Yukawa one-component plasmas2019In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 26, no 5, article id 053705Article in journal (Refereed)
    Abstract [en]

    In numerous realizations of complex plasmas, dust-dust interactions are characterized by two screening lengths and are thus better described by a combination of Yukawa potentials. The present work investigates the static correlations and the thermodynamics of repulsive dense bi-Yukawa fluids based on the fact that such strongly coupled systems exhibit isomorph invariance. The strong virial-potential energy correlations are demonstrated with the aid of molecular dynamics simulations, an accurate analytical expression for the isomorph family of curves is obtained, and an empirical expression for the fluid-solid phase-coexistence line is proposed. The isomorph-based empirically modified hypernetted-chain approach, grounded on the ansatz of isomorph invariant bridge functions, is then extended to such systems and the resulting structural properties show an excellent agreement with the results of computer simulations. A simple and accurate closed-form expression is obtained for the excess internal energy of dense bi-Yukawa fluids by capitalizing on the compact parameterization offered by the Rosenfeld-Tarazona decomposition in combination with the Rosenfeld scaling, which opens up the energy route to thermodynamics.

  • 18.
    Tolias, Panagiotis
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Castello, F. Lucco
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Isomorph-based empirically modified hypernetted-chain approach for strongly coupled Yukawa one-component plasmas2019In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 26, no 4, article id 043703Article in journal (Refereed)
    Abstract [en]

    Isomorph theory is employed in order to establish a mapping between the bridge function of Coulomb and Yukawa one-component plasmas. Within an exact invariance ansatz for the bridge functions and by capitalizing on the availability of simulation-extracted Coulomb bridge functions, an analytical Yukawa bridge function is derived which is inserted into the integral theory framework. In spite of its simplicity and computational speed, the proposed integral approach exhibits an excellent agreement with computer simulations of dense Yukawa liquids without invoking adjustable parameters. 

  • 19. Li, B.
    et al.
    Han, D. -S
    Hu, Z. -J
    Hu, H. -Q
    Liu, J. -J
    Dai, L.
    Liu, H.
    Escoubet, C. P.
    Dunlop, M. W.
    Ergun, R. E.
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Torbert, R. B.
    Russell, C. T.
    Magnetospheric Multiscale Observations of ULF Waves and Correlated Low-Energy Ion Monoenergetic Acceleration2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402Article in journal (Refereed)
    Abstract [en]

    Low-energy ions of ionospheric origin with energies below 10s of electron volt dominate most of the volume and mass of the terrestrial magnetosphere. However, sunlit spacecraft often become positively charged to several 10s of volts, which prevents low-energy ions from reaching the particle detectors on the spacecraft. Magnetospheric Multiscale spacecraft (MMS) observations show that ultralow-frequency (ULF) waves drive low-energy ions to drift in the E × B direction with a drift velocity equal to V E × B , and low-energy ions were accelerated to sufficient total energy to be measured by the MMS/Fast Plasma Investigation Dual Ion Spectrometers. The maximum low-energy ion energy flux peak seen in MMS1's dual ion spectrometer measurements agreed well with the theoretical calculation of H + ion E × B drift energy. The density of ions in the energy range below minimum energy threshold was between 1 and 3 cm −3 in the magnetosphere subsolar region in this event.

  • 20.
    Steinvall, K.
    et al.
    Swedish Inst Space Phys, Uppsala, Sweden.;Uppsala Univ, Dept Phys & Astron, Uppsala, Sweden..
    Khotyaintsev, Yu. V.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Graham, D. B.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Vaivads, Andris
    Swedish Inst Space Phys, Uppsala, Sweden..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Multispacecraft Analysis of Electron Holes2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 1, p. 55-63Article in journal (Refereed)
    Abstract [en]

    Electron holes (EHs) are nonlinear electrostatic structures in plasmas. Most previous in situ studies of EHs have been limited to single- and two-spacecraft methods. We present statistics of EHs observed by Magnetospheric Multiscale on the magnetospheric side of the magnetopause during October 2016 when the spacecraft separation was around 6km. Each EH is observed by all four spacecraft, allowing EH properties to be determined with unprecedented accuracy. We find that the parallel length scale, l(vertical bar), scales with the Debye length. The EHs can be separated into three groups of speed and potential based on their coupling to ions. We present a method for calculating the perpendicular length scale, l. The method can be applied to a small subset of the observed EHs for which we find shapes ranging from almost spherical to more oblate. For the remaining EHs we use statistical arguments to find l/l(vertical bar)approximate to 5, implying dominance of oblate EHs. Plain Language Summary Electron holes are positively charged structures moving along the magnetic field and are frequently observed in space plasmas in relation to strong currents and electron beams. Electron holes interact with the plasma, leading to electron heating and scattering. In order to understand the effect of these electron holes, we need to accurately determine their properties, such as velocity, length scale, and potential. Most earlier studies have relied on single- or two-spacecraft methods to analyze electron holes. In this study we use the four satellites of the Magnetospheric Multiscale mission to analyze 236 electron holes with unprecedented accuracy. We find that the holes can be divided into three distinct groups with different properties. Additionally, we calculate the width of individual electron holes, finding that they are typically much wider than long, resembling pancakes.

  • 21.
    Zhou, M.
    et al.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang, Jiangxi, Peoples R China..
    Deng, X. H.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang, Jiangxi, Peoples R China..
    Zhong, Z. H.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang, Jiangxi, Peoples R China..
    Pang, Y.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang, Jiangxi, Peoples R China..
    Tang, R. X.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang, Jiangxi, Peoples R China..
    El-Alaoui, M.
    UCLA, Dept Phys & Astron, Los Angeles, CA USA..
    Walker, R. J.
    UCLA, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Russell, C. T.
    UCLA, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Lapenta, G.
    Katholieke Univ Leuven, Dept Math, Ctr Plasma Astrophys, Leuven, Belgium..
    Strangeway, R. J.
    UCLA, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Torbert, R. B.
    Univ New Hampshire, Durham, NH 03824 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Paterson, W. R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Khotyaintsev, Y. V.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Ergun, R. E.
    Univ Colorado LASP, Boulder, CO USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Observations of an Electron Diffusion Region in Symmetric Reconnection with Weak Guide Field2019In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 870, no 1, article id 34Article in journal (Refereed)
    Abstract [en]

    The Magnetospheric Multiscale spacecraft encountered an electron diffusion region (EDR) in a symmetric reconnection in the Earth's magnetotail. The EDR contained a guide field of about 2 nT, which was 13% of the magnetic field in the inflow region, and its thickness was about 2 local electron inertial lengths. Intense energy dissipation, a super-Alfvenic electron jet, electron nongyrotropy, and crescent-shaped electron velocity distributions were observed in association with this EDR. These features are similar to those of the EDRs in asymmetric reconnection at the dayside magnetopause. Electrons gained about 50% of their energy from the immediate upstream to the EDR. Crescent electron distributions were seen at the boundary of the EDR, while highly curved magnetic field lines inside the EDR may have gyrotropized the electrons. The EDR was characterized by a parallel current that was carried by antiparallel drifting electrons that were probably accelerated by a parallel electric field along the guide field. These results reveal the essential electron physics of the EDR and provide a significant example of an EDR in symmetric reconnection with a weak guide field.

  • 22.
    Stawarz, J. E.
    et al.
    Imperial Coll London, Dept Phys, London, England..
    Eastwood, J. P.
    Imperial Coll London, Dept Phys, London, England..
    Phan, T. D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Gingell, I. L.
    Imperial Coll London, Dept Phys, London, England..
    Shay, M. A.
    Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Ergun, R. E.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Le Contel, O.
    Univ Paris Sud, Lab Phys Plasmas, CNRS, Ecole Polytech,Sorbonne Univ,Observ Paris, Paris, France..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Strangeway, R. J.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Torbert, R. B.
    Univ New Hampshire, Dept Phys, Durham, NH 03824 USA..
    Argall, M. R.
    Univ New Hampshire, Dept Phys, Durham, NH 03824 USA..
    Fischer, D.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Magnes, W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Franci, L.
    Queen Mary Univ London, Sch Phys & Astron, London, England..
    Properties of the Turbulence Associated with Electron-only Magnetic Reconnection in Earth's Magnetosheath2019In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 877, no 2, article id L37Article in journal (Refereed)
    Abstract [en]

    Turbulent plasmas generate intense current structures, which have long been suggested as magnetic reconnection sites. Recent Magnetospheric Multiscale observations in Earth's magnetosheath revealed a novel form of reconnection where the dynamics only couple to electrons, without ion involvement. It was suggested that such dynamics were driven by magnetosheath turbulence. In this study, the fluctuations are examined to determine the properties of the turbulence and if a signature of reconnection is present in the turbulence statistics. The study reveals statistical properties consistent with plasma turbulence with a correlation length of similar to 10 ion inertial lengths. When reconnection is more prevalent, a steepening of the magnetic spectrum occurs at the length scale of the reconnecting current sheets. The statistics of intense currents suggest the prevalence of electron-scale current sheets favorable for electron reconnection. The results support the hypothesis that electron reconnection is driven by turbulence and highlight diagnostics that may provide insight into reconnection in other turbulent plasmas.

  • 23.
    Oieroset, M.
    et al.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. rake, J. F..
    Phan, T. D.
    Drake, J. F.
    Eastwood, J. P.
    Fuselier, S. A.
    Strangeway, R. J.
    Haggerty, C.
    Shay, M. A.
    Oka, M.
    Wang, S.
    Chen, L-J
    Kacem, I
    Lavraud, B.
    Angelopoulos, V
    Burch, J. L.
    Torbert, R. B.
    Ergun, R. E.
    Khotyaintsev, Y.
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Gershman, D. J.
    Giles, B. L.
    Pollock, C.
    Moore, T. E.
    Russell, C. T.
    Saito, Y.
    Avanov, L. A.
    Paterson, W.
    Reconnection With Magnetic Flux Pileup at the Interface of Converging ts at the Magnetopause2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 4, p. 1937-1946Article in journal (Refereed)
    Abstract [en]

    We report Magnetospheric Multiscale observations of reconnection in a in current sheet at the interface of interlinked flux tubes carried by nverging reconnection jets at Earth's magnetopause. The ion skin pth-scale width of the interface current sheet and the non-frozen-in ns indicate that Magnetospheric Multiscale crossed the reconnection yer near the X-line, through the ion diffusion region. Significant leup of the reconnecting component of the magnetic field in this and ree other events on approach to the interface current sheet was companied by an increase in magnetic shear and decrease in , leading conditions favorable for reconnection at the interface current sheet. e pileup also led to enhanced available magnetic energy per particle d strong electron heating. The observations shed light on the olution and energy release in 3-D systems with multiple reconnection tes. ain Language Summary The Earth and the solar wind magnetic fields terconnect through a process called magnetic reconnection. The newly connected magnetic field lines are strongly bent and accelerate rticles, similar to a rubber band in a slingshot. In this paper we ve used observations from NASA's Magnetospheric MultiScale spacecraft investigate what happens when two of these slingshot-like magnetic eld lines move toward each other and get tangled up. We found that the o bent magnetic field lines tend to orient themselves perpendicular to ch other as they become interlinked and stretched, similar to what bber bands would do. This reorientation allows the interlinked gnetic fields to reconnect again, releasing part of the built-up gnetic energy as strong electron heating. The results are important cause they show how interlinked magnetic fields, which occur in many lar and astrophysics contexts, reconnect and produce enhanced electron ating, something that was not understood before.

  • 24.
    Kateb, Movaffaq
    et al.
    Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Hajihoseini, Hamidreza
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland.
    Ingvarsson, Snorri
    Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Role of ionization fraction on the surface roughness, density, and interface mixing of the films deposited by thermal evaporation, dc magnetron sputtering, and HiPIMS: An atomistic simulation2019In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 37, no 3, article id 031306Article in journal (Refereed)
    Abstract [en]

    The effect of ionization fraction on the epitaxial growth of Cu film on Cu (111) substrate at room temperature is explored. Three deposition methods, thermal evaporation, dc magnetron sputtering (dcMS), and high power impulse magnetron sputtering (HiPIMS) are compared. Three deposition conditions, i.e., fully neutral, 50% ionized, and 100% ionized flux were considered thermal evaporation, dcMS, and HiPIMS, respectively, for similar to 20 000 adatoms. It is shown that higher ionization fraction of the deposition flux leads to smoother surfaces by two major mechanisms, i.e., decreasing clustering in the vapor phase and bicollision of high energy ions at the film surface. The bicollision event consists of local amorphization which fills the gaps between islands followed by crystallization due to secondary collisions. The bicollision events are found to be very important to prevent island growth to become dominant and increase the surface roughness. Regardless of the deposition method, epitaxial Cu thin films suffer from stacking fault areas (twin boundaries) in agreement with recent experimental results. Thermal evaporation and dcMS deposition present negligible interface mixing while HiPIMS deposition presents considerable interface mixing. Published by the AVS.

  • 25.
    Nakamura, Rumi
    et al.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Genestreti, Kevin J.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.;Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Naltamora, Takuma
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Baumjohann, Wolfgang
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Varsani, Ali
    Univ Coll London, Mullard Space Sci Lab, Dorking, Surrey, England..
    Nagai, Tsugunobu
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Sagamihara, Kanagawa, Japan..
    Bessho, Naoki
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Burch, James L.
    Southwest Res Inst, San Antonio, TX USA..
    Denton, Richard E.
    Dartmouth Coll, Dept Phys & Astron, Hanover, NH 03755 USA..
    Eastwood, Jonathan P.
    Imperial Coll London, Blackett Lab, London, England..
    Ergun, Robert E.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO USA..
    Gershman, Daniel J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Giles, Arbara L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Hasegaw, Iroshi
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Sagamihara, Kanagawa, Japan..
    Hesse, Michael
    Univ Bergen, Dept Phys & Technol, Bergen, Norway..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Russell, Hristopher T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Stawarz, Ulia E.
    Imperial Coll London, Blackett Lab, London, England..
    Strangeway, Robert J.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Torber, Roy B.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA.;Southwest Res Inst, San Antonio, TX USA..
    Structure of the Current Sheet in the 11 July 2017 Electron Diffusion Region Event2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 2, p. 1173-1186Article in journal (Refereed)
    Abstract [en]

    The structure of the current sheet along the Magnetospheric Multiscale (MMS) orbit is examined during the 11 July 2017 Electron Diffusion Region (EDR) event. The location of MMS relative to the X-line is deduced and used to obtain the spatial changes in the electron parameters. The electron velocity gradient values are used to estimate the reconnection electric field sustained by nongyrotropic pressure. It is shown that the observations are consistent with theoretical expectations for an inner EDR in 2-D reconnection. That is, the magnetic field gradient scale, where the electric field due to electron nongyrotropic pressure dominates, is comparable to the gyroscale of the thermal electrons at the edge of the inner EDR. Our approximation of the MMS observations using a steady state, quasi-2-D, tailward retreating X-line was valid only for about 1.4 s. This suggests that the inner EDR is localized; that is, electron outflow jet braking takes place within an ion inertia scale from the X-line. The existence of multiple events or current sheet processes outside the EDR may play an important role in the geometry of reconnection in the near-Earth magnetotail. Plain Language Summary Magnetic reconnection is the process by which magnetic field lines coming from one region are broken and reconnected with magnetic field lines coming from another region. The simplest descriptions of magnetic reconnection are two dimensional, and a number of theoretical predictions have been made using the two-dimensional assumption. We study a magnetic reconnection event observed by the Magnetospheric Multiscale spacecraft on 11 July 2017 and find approximate agreement between the observations and the predictions of a two-dimensional model. The agreement includes the scale size of the reconnection region, details of the particle orbits, and the rate of reconnection.

  • 26.
    Tolias, Panagiotis
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    De Angeli, M.
    CNR, Ist Fis Plasma, Via Corsi 53, I-20125 Milan, Italy..
    Riva, G.
    CNR, Inst Condensed Matter Chem & Energy Technol, Via Cozzi 53, I-20125 Milan, Italy..
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Daminelli, G.
    CNR, Inst Condensed Matter Chem & Energy Technol, Via Cozzi 53, I-20125 Milan, Italy..
    Laguardia, L.
    CNR, Ist Fis Plasma, Via Corsi 53, I-20125 Milan, Italy..
    Pedron, M.
    CNR, Ist Fis Plasma, Via Corsi 53, I-20125 Milan, Italy..
    Ripamonti, D.
    CNR, Inst Condensed Matter Chem & Energy Technol, Via Cozzi 53, I-20125 Milan, Italy..
    Uccello, A.
    CNR, Ist Fis Plasma, Via Corsi 53, I-20125 Milan, Italy..
    Vassallo, E.
    CNR, Ist Fis Plasma, Via Corsi 53, I-20125 Milan, Italy..
    The adhesion of tungsten dust on plasma-exposed tungsten surfaces2019In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 18, p. 18-22Article in journal (Refereed)
    Abstract [en]

    The adhesion of tungsten dust is measured on plasma-exposed and non-exposed tungsten substrates with the electrostatic detachment method. Tungsten substrates of comparable surface roughness have been exposed to the deuterium plasmas of the GyM linear device and the argon plasmas of rf glow discharges under conditions which invariably modify the surface composition due to physical sputtering. The adhesion has been systematically characterized for different spherical nearly monodisperse dust populations. Independent of the dust size, an approximate 50% post-exposure reduction of the average and spread of the adhesive force has been consistently observed and attributed to surface chemistry modifications.

  • 27.
    Yao, S. T.
    et al.
    Shandong Univ, Inst Space Sci, Shandong Prov Key Lab Opt Astron & Solar Terr Env, Weihai, Peoples R China.;Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Shi, Q. Q.
    Shandong Univ, Inst Space Sci, Shandong Prov Key Lab Opt Astron & Solar Terr Env, Weihai, Peoples R China..
    Yao, Z. H.
    UCL, Mullard Space Sci Lab, London, England.;Univ Liege, STAR Inst, Lab Phys Atmospher & Planetaire, Liege, Belgium..
    Li, J. X.
    Univ Calif Los Angeles, Dept Atmospher & Ocean Sci, Los Angeles, CA USA..
    Yue, C.
    Univ Calif Los Angeles, Dept Atmospher & Ocean Sci, Los Angeles, CA USA..
    Tao, X.
    Univ Sci & Technol China, Dept Geophys & Planetary Sci, CAS Key Lab Geospace Environm, Hefei, Anhui, Peoples R China..
    Degeling, A. W.
    Shandong Univ, Inst Space Sci, Shandong Prov Key Lab Opt Astron & Solar Terr Env, Weihai, Peoples R China..
    Zong, Q. G.
    Peking Univ, Sch Earth & Space Sci, Beijing, Peoples R China..
    Wang, X. G.
    Harbin Inst Technol, Dept Phys, Harbin, Heilongjiang, Peoples R China..
    Tian, A. M.
    Shandong Univ, Inst Space Sci, Shandong Prov Key Lab Opt Astron & Solar Terr Env, Weihai, Peoples R China..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Zhou, X. Z.
    Peking Univ, Sch Earth & Space Sci, Beijing, Peoples R China..
    Guo, R. L.
    Chinese Acad Sci, Inst Geol & Geophys, Key Lab Earth & Planetary Phys, Beijing, Peoples R China..
    Rae, I. J.
    UCL, Mullard Space Sci Lab, London, England..
    Fu, H. S.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China..
    Zhang, H.
    Univ Alaska Fairbanks, Phys Dept, Fairbanks, AK USA.;Univ Alaska Fairbanks, Geophys Inst, Fairbanks, AK 99775 USA..
    Li, L.
    Harbin Inst Technol, Dept Phys, Harbin, Heilongjiang, Peoples R China..
    Le Contel, O.
    Univ Paris Sud, Sorbonne Univ, Lab Phys Plasmas, Observ Paris,Ecole Polytech,CNRS,UMR7648, Paris, France..
    Torbert, R. B.
    Univ New Hampshire, Dept Phys, Durham, NH 03824 USA..
    Ergun, R. E.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Pollock, C. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Waves in Kinetic-Scale Magnetic Dips: MMS Observations in the Magnetosheath2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 2, p. 523-533Article in journal (Refereed)
    Abstract [en]

    Kinetic scale magnetic dips (KSMDs), with a significant depression in magnetic field strength, and scale length close to and less than one proton gyroradius, were reported in the turbulent plasmas both in recent observation and numerical simulation studies. These KSMDs likely play important roles in energy conversion and dissipation. In this study, we present observations of the KSMDs that are labeled whistler mode waves, electrostatic solitary waves, and electron cyclotron waves in the magnetosheath. The observations suggest that electron temperature anisotropy or beams within KSMD structures provide free energy to generate these waves. In addition, the occurrence rates of the waves are higher in the center of the magnetic dips than at their edges, implying that the KSMDs might be the origin of various kinds of waves. We suggest that the KSMDs could provide favorable conditions for the generation of waves and transfer energy to the waves in turbulent magnetosheath plasmas. Plain Language Summary The Earth's magnetosheath is a turbulent plasma environment where energy conversion, particle acceleration, and mass and momentum transport take place. Many of these key processes involve kinetic-scale physics. However, in-depth studies from previous missions are limited by their lower spacecraft data resolution. The recent Magnetospheric Multiscale (MMS) mission provides us with a large amount of high-temporal cadence data for studying kinetic-scale physics in the magnetosheath. In this study, we report whistler mode waves, electrostatic solitary waves and electron cyclotron waves within kinetic-scale magnetic dips (KSMDs) that can be generated in the turbulent magnetosheath. These waves could be excited by electron temperature anisotropy or beams. As is well known, plasma waves are important processes in converting energy, accelerating and scattering electrons and ions, and modifying the distributions of charged particles. If plasma instabilities develop within the KSMDs, the resulting waves could absorb free energy from plasma particles and may propagate out of the KSMDs. Thus, our discoveries could significantly advance the understanding of energy conversion and dissipation for kinetic-scale turbulence. This study provides a new reference not only for observations in space physics but also for related basic plasma theories and numerical simulations.

  • 28.
    Ren, Y.
    et al.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Dai, L.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Li, W.
    Boston Univ, Ctr Space Phys, Boston, MA 02215 USA..
    Tao, X.
    Univ Sci & Technol China, Dept Geophys & Planetary Sci, CAS Key Lab Geospace Environm, Hefei, Anhui, Peoples R China..
    Wang, C.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Tang, B.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Planetol, CNRS, UPS,CNES, Toulouse, France..
    Wu, Y.
    Univ Sci & Technol China, Dept Geophys & Planetary Sci, CAS Key Lab Geospace Environm, Hefei, Anhui, Peoples R China..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Le Contel, O.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, Paris, France..
    Torbert, R. B.
    Univ New Hampshire, Dept Phys, Durham, NH 03824 USA..
    Russell, C. T.
    Univ Calif Los Angeles, Earth & Planetary Sci, Los Angeles, CA USA..
    Strangeway, R. J.
    Univ Calif Los Angeles, Earth & Planetary Sci, Los Angeles, CA USA..
    Ergun, R. E.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China.;Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Whistler Waves Driven by Field-Aligned Streaming Electrons in the Near-Earth Magnetotail Reconnection2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 10, p. 5045-5054Article in journal (Refereed)
    Abstract [en]

    We analyze Magnetospheric Multiscale Mission observations of whistler waves and associated electron field-aligned crescent distribution in the vicinity of the magnetotail near-Earth X-line. The whistler waves propagate outward from the X-line in the neutral sheet. The associated field-aligned streaming electrons exhibit a crescent-like shape, with an inverse slope (df/d vertical bar v(parallel to)vertical bar > 0) at 1-5 keV. The parallel phase velocity of the waves is in the range (1-5 keV) of the inverse slope of the field-aligned crescents in the velocity space. We demonstrate that the observed whistler waves are driven by the electron field-aligned crescents through Landau resonance. The cyclotron resonance is at the high-energy tail with negligible free energy of pitch angle anisotropy in these events.

  • 29.
    Sun, W. J.
    et al.
    Chinese Acad Sci, Inst Geol & Geophys, Key Lab Earth & Planetary Phys, Beijing, Peoples R China.;Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI 48109 USA.;Peking Univ, Sch Earth & Space Sci, Beijing, Peoples R China.;Chinese Acad Sci, Key Lab Lunar & Deep Space Explorat, Natl Astron Observ, Beijing, Peoples R China..
    Slavin, J. A.
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI 48109 USA..
    Dewey, R. M.
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI 48109 USA..
    Raines, J. M.
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI 48109 USA..
    Fu, S. Y.
    Peking Univ, Sch Earth & Space Sci, Beijing, Peoples R China..
    Wei, Y.
    Chinese Acad Sci, Inst Geol & Geophys, Key Lab Earth & Planetary Phys, Beijing, Peoples R China..
    Karlsson, Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Poh, G. K.
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI 48109 USA..
    Jia, X.
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI 48109 USA..
    Gershman, D. J.
    NASA, Geospace Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Zong, Q. G.
    Peking Univ, Sch Earth & Space Sci, Beijing, Peoples R China..
    Wan, W. X.
    Chinese Acad Sci, Inst Geol & Geophys, Key Lab Earth & Planetary Phys, Beijing, Peoples R China..
    Shi, Q. Q.
    Shandong Univ, Sch Space Sci & Phys, Shandong Prov Key Lab Opt Astron & Solar Terr Env, Weihai, Peoples R China..
    Pu, Z. Y.
    Peking Univ, Sch Earth & Space Sci, Beijing, Peoples R China..
    Zhao, D.
    Peking Univ, Sch Earth & Space Sci, Beijing, Peoples R China..
    A Comparative Study of the Proton Properties of Magnetospheric Substorms at Earth and Mercury in the Near Magnetotail2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 16, p. 7933-7941Article in journal (Refereed)
    Abstract [en]

    The variations of plasma sheet proton properties during magnetospheric substorms at Earth and Mercury are comparatively studied. This study utilizes kappa distributions to interpret proton properties at both planets. Proton number densities are found to be around an order of magnitude higher, temperatures several times smaller, and kappa values broader at Mercury than at Earth. Protons become denser and cooler during the growth phase, and are depleted and heated after the dipolarizations in both magnetospheres. The changes of kappa at Earth are generally small (<20%), indicating that spectrum-preserving processes, like adiabatic betatron acceleration, play an important role there, while variations of kappa at Mercury are large (>60%), indicating the importance of spectrum-altering processes there, such as acceleration due to nonadiabatic cross-tail particle motions and wave-particle interactions. This comparative study reveals important intrinsic properties on the energization of protons in both magnetospheres. Plain Language Summary Earth and Mercury are the only two planets possessing global intrinsic magnetic fields among the four inner planets, which are Mercury, Venus, Earth, and Mars, within the solar system. The interactions between the intrinsic magnetic fields and the continual flow of high-speed solar wind from the Sun form similar magnetospheres at the two planets, although the scale of the magnetosphere is much smaller at Mercury than at Earth. Magnetospheric substorms, a result of solar wind-magnetosphere coupling, occur in both magnetospheres. Comparative study of a similar process between different planets is meaningful as it can help us in understanding the specific process further as well as help us in understanding the intrinsic properties of the magnetospheres. This research paper characterizes the proton properties of magnetospheric substorms of both planets, revealing that different mechanisms control the behavior of protons during the magnetospheric substorms of the two planets.

  • 30.
    Tolias, Panagiotis
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Riva, G.
    De Angeli, M.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Daminelli, G.
    Lungu, C. P.
    Porosnicu, C.
    Adhesive force distributions for tungsten dust deposited on bulk tungsten and beryllium-coated tungsten surfaces2018In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 15, p. 55-63Article in journal (Refereed)
    Abstract [en]

    Comprehensive measurements of the adhesive force for tungsten dust adhered to tungsten surfaces have been performed with the electrostatic detachment method. Monodisperse spherical dust has been deposited with gas dynamics techniques or with gravity mimicking adhesion as it naturally occurs in tokamaks. The adhesive force is confirmed to follow the log-normal distribution and empirical correlations are proposed for the size-dependence of its mean and standard deviation. Systematic differences are observed between the two deposition methods and attributed to plastic deformation during sticking impacts. The presence of thin beryllium coatings on tungsten surfaces is demonstrated to barely affect adhesion.

  • 31.
    Wang, Rongsheng
    et al.
    Univ Sci & Technol China, Dept Geophys & Planetary Sci, CAS Key Lab Geospace Environm, Hefei, Anhui, Peoples R China..
    Lu, Quanming
    Univ Sci & Technol China, Dept Geophys & Planetary Sci, CAS Key Lab Geospace Environm, Hefei, Anhui, Peoples R China..
    Nakamura, Rumi
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Baumjohann, Wolfgang
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Huang, Can
    Univ Sci & Technol China, Dept Geophys & Planetary Sci, CAS Key Lab Geospace Environm, Hefei, Anhui, Peoples R China..
    Russell, Christopher T.
    Univ Calif Los Angeles, Earth Planetary & Space Sci, Los Angeles, CA USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Pollock, Craig J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Gershman, Dan
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Ergun, R. E.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA..
    Wang, Shui
    Univ Sci & Technol China, Dept Geophys & Planetary Sci, CAS Key Lab Geospace Environm, Hefei, Anhui, Peoples R China..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Giles, Barbara
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    An Electron-Scale Current Sheet Without Bursty Reconnection Signatures Observed in the Near-Earth Tail2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 10, p. 4542-4549Article in journal (Refereed)
    Abstract [en]

    Observations of a current sheet as thin as the electron scale are extremely rare in the near-Earth magnetotail. By measurement from the novel Magnetospheric Multiscale mission in the near-Earth magnetotail, we identified such an electron-scale current sheet and determined its detailed properties. The electron current sheet was bifurcated, with a half-thickness of nine electron inertial lengths, and was sandwiched between the Hall field. Because of the strong Hall electric field, the super-Alfvenic electron bulk flows were created mainly by the electric field drift, leading to the generation of the strong electron current. Inevitably, a bifurcated current sheet was formed since the Hall electric field was close to zero at the center of the current sheet. Inside the electron current sheet, the electrons were significantly heated while the ion temperature showed no change. The ions kept moving at a low speed, which was not affected by this electron current sheet. The energy dissipation was negligible inside the current sheet. The observations indicate that a thin current sheet, even as thin as electron scale, is not the sufficient condition for triggering bursty reconnection.

  • 32. Hamrin, M.
    et al.
    Gunell, H.
    Lindkvist, J.
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Ergun, R. E.
    Giles, B. L.
    Bow Shock Generator Current Systems: MMS Observations of Possible Current Closure2018In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 1, p. 242-258Article in journal (Refereed)
    Abstract [en]

    We use data from the first two dayside seasons of the Magnetospheric Multiscale (MMS) mission to study current systems associated with quasi-perpendicular bow shocks of generator type. We have analyzed 154 MMS bow shock crossings near the equatorial plane. We compute the current density during the crossings and conclude that the component perpendicular to the shock normal (J) is consistent with a pileup of the interplanetary magnetic field (IMF) inside the magnetosheath. For predominantly southward IMF, we observe a component J(n) parallel (antiparallel) to the normal for GSM gamma > 0 (<0), and oppositely directed for northward IMF. This indicates current closure across the equatorial magnetosheath, and it is observed for IMF clock angles near 0 degrees and 180 degrees. To our knowledge, these are the first observational evidence for bow shock current closure across the magnetosheath. Since we observe no clear signatures of vertical bar J(perpendicular to)vertical bar decreasing toward large vertical bar Y vertical bar we suggest that the main region of current closure is further tailward, outside MMS probing region. For IMF clock angles near 90 degrees, we find indications of the current system being tilted toward the north-south direction, obtaining a significant J(z) component, and we suggest that the current closes off the equatorial plane at higher latitudes where the spacecraft are not probing. The observations are complicated for several reasons. For example, variations in the solar wind and the magnetospheric currents and loads affect the closure, and J(n) is distributed over large regions, making it difficult to resolve inside the magnetosheath proper.

  • 33.
    Ekeroth, Sebastian
    et al.
    Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden..
    Munger, E. Peter
    Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden..
    Boyd, Robert
    Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden..
    Ekspong, Joakim
    Umea Univ, Dept Phys, SE-90187 Umea, Sweden..
    Wagberg, Thomas
    Umea Univ, Dept Phys, SE-90187 Umea, Sweden..
    Edman, Ludvig
    Umea Univ, Dept Phys, SE-90187 Umea, Sweden..
    Brenning, Nils
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden.
    Helmersson, Ulf
    Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden..
    Catalytic Nanotruss Structures Realized by Magnetic Self-Assembly in Pulsed Plasma2018In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, no 5, p. 3132-3137Article in journal (Refereed)
    Abstract [en]

    Tunable nanostructures that feature a high surface area are firmly attached to a conducting substrate and can be fabricated efficiently over significant areas, which are of interest for a wide variety of applications in, for instance, energy storage and catalysis. We present a novel approach to fabricate Fe nanoparticles using a pulsed-plasma process and their subsequent guidance and self-organization into well-defined nanostructures on a substrate of choice by the use of an external magnetic field. A systematic analysis and study of the growth procedure demonstrate that nondesired nanoparticle agglomeration in the plasma phase is hindered by electrostatic repulsion, that a polydisperse nanoparticle distribution is a consequence of the magnetic collection, and that the formation of highly networked nanotruss structures is a direct result of the polydisperse nanoparticle distribution. The nanoparticles in the nanotruss are strongly connected, and their outer surfaces are covered with a 2 nm layer of iron oxide. A 10 mu m thick nanotruss structure was grown on a lightweight, flexible and conducting carbon-paper substrate, which enabled the efficient production of H-2 gas from water splitting at a low overpotential of 210 mV and at a current density of 10 mA/cm(2).

  • 34.
    Vaverka, Jakub
    et al.
    Umea Univ, Dept Phys, Umea, Sweden.;Natl Inst Polar Res, Tachikawa, Tokyo, Japan.;Charles Univ Prague, Fac Math & Phys, Prague, Czech Republic..
    Nakamura, Takuji
    Natl Inst Polar Res, Tachikawa, Tokyo, Japan..
    Kero, Johan
    Swedish Inst Space Phys, Kiruna, Sweden..
    Mann, Ingrid
    Arctic Univ Norway, Tromso, Norway..
    De Spiegeleer, Alexandre
    Umea Univ, Dept Phys, Umea, Sweden..
    Hamrin, Maria
    Umea Univ, Dept Phys, Umea, Sweden..
    Norberg, Carol
    Umea Univ, Dept Phys, Umea, Sweden.;Swedish Inst Space Phys, Kiruna, Sweden..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Pellinen-Wannberg, Asta
    Umea Univ, Dept Phys, Umea, Sweden.;Swedish Inst Space Phys, Kiruna, Sweden..
    Comparison of Dust Impact and Solitary Wave Signatures Detected by Multiple Electric Field Antennas Onboard the MMS Spacecraft2018In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 8, p. 6119-6129Article in journal (Refereed)
    Abstract [en]

    Dust impact detection by electric field instruments is a relatively new method. However, the influence of dust impacts on electric field measurements is not completely understood and explained. A better understanding is very important for reliable dust impact identification, especially in environments with low dust impact rate. Using data from Earth-orbiting Magnetospheric Multiscale mission (MMS) spacecraft, we present a study of various pulses detected simultaneously by multiple electric field antennas in the monopole (probe-to-spacecraft potential measurement) and dipole (probe-to-probe potential measurement) configurations. The study includes data obtained during an impact of a millimeter-sized object. We show that the identification of dust impacts by a single antenna is a very challenging issue in environments where solitary waves are commonly present and that some pulses can be easily misinterpreted as dust impacts. We used data from multiple antennas to distinguish between changes in the spacecraft potential (dust impact) and structures in the ambient plasma or electric field. Our results indicate that an impact cloud is in some cases able to influence the potential of the electric field antenna during its expansion.

  • 35.
    Kateb, Movaffaq
    et al.
    Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Hajihoseini, Hamidreza
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland.
    Ingvarsson, Snorri
    Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Comparison of magnetic and structural properties of permalloy Ni80Fe20 grown by dc and high power impulse magnetron sputtering2018In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 51, no 28, article id 285005Article in journal (Refereed)
    Abstract [en]

    We study the microstructure and magnetic properties of Ni80Fe20 thin films grown by high power impulse magnetron sputtering (HiPIMS), and compare with films grown by dc magnetron sputtering (dcMS). The films were grown under a tilt angle of 35 degrees to identical thickness of 37 nm using both techniques, at different pressure (0.13-0.73 Pa) and substrate temperature (room temperature and 100 degrees C). All of our films display effective in-plane uniaxial anisotropy with square easy axis and linear hard axis magnetization traces. X-ray diffraction reveals that there is very little change in grain size within the pressure and temperature ranges explored. However, variations in film density, obtained by x-ray reflectivity measurements, with pressure have a significant effect on magnetic properties such as anisotropy field (H-k) and coercivity (H-c). Depositions where adatom energy is high produce dense films, while low adatom energy results in void-rich films with higher H-k and H-c. The latter applies to our dcMS deposited films at room temperature and high pressure. However, the HiPIMS deposition method gives higher adatom energy than the dcMS and results in dense films with low H-k and H-c. The surface roughness is found to increase with increased pressure, in all cases, however it showed negligible contribution to the increase in H-k, and H-c.

  • 36.
    Roth, Lorenz
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Constraints on water vapor and sulfur dioxide at Ceres: Exploiting the sensitivity of the Hubble Space Telescope2018In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 305, p. 149-159Article in journal (Refereed)
    Abstract [en]

    Far-ultraviolet observations of dwarf-planet (1) Ceres were obtained on several occasions in 2015 and 2016 by the Cosmic Origins Spectrograph (COS) and the Space Telescope Imaging Spectrograph (STIS), both on board the Hubble Space Telescope (HST). We report a search for neutral gas emissions at hydrogen, oxygen and sulfur lines around Ceres from a potential teneous exosphere. No detectable exosphere emissions are present in any of the analyzed HST observations. We apply analytical models to relate the derived upper limits for the atomic species to a water exosphere (for H and O) and a sulfur dioxide exosphere (for S and O), respectively. The H and O upper limits constrain the H2O production rate at the surface to (2-4) x 10(26) molecules s(-1) or lower, similar to or slightly larger than previous detections and upper limits. With low fluxes of energetic protons measured in the solar wind prior to the HST observations and the obtained non-detections, an assessment of the recently suggested sputter-generated water exosphere during solar energetic particle events is not possible. Investigating a sulfur dioxide-based exosphere, we find that the O and S upper limits constrain the SO2 density at the surface to values similar to 10(10) times lower than the equilibrium vapor pressure density. This result implies that SO2 is not present on Ceres' sunlit surface, contrary to previous findings in HST ultraviolet reflectance spectra but in agreement with the absence of SO2 infrared spectral features as observed by the Dawn spacecraft.

  • 37.
    Pitkanen, T.
    et al.
    Shandong Univ, Inst Space Sci, Weihai, Peoples R China.;Umea Univ, Dept Phys, Umea, Sweden..
    Kullen, Anita
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Shi, Q. Q.
    Shandong Univ, Inst Space Sci, Weihai, Peoples R China..
    Hamrin, M.
    Umea Univ, Dept Phys, Umea, Sweden..
    De Spiegeleer, A.
    Umea Univ, Dept Phys, Umea, Sweden..
    Nishimura, Y.
    Boston Univ, Ctr Space Phys, Boston, MA 02215 USA..
    Convection Electric Field and Plasma Convection in a Twisted Magnetotail: A THEMIS Case Study 1-2 January 20092018In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 9, p. 7486-7497Article in journal (Refereed)
    Abstract [en]

    We investigate THEMIS satellite measurements made in a tail-aligned constellation during a time interval on 1-2 January 2009, which has previously been attributed to an interval of an interplanetary magnetic fieldB(y)-driven magnetotail twisting. We find evidence for that the orientation of the convection electric field in the tail is twist-mode dependent. For earthward flow and a negative twist (induced tail B-y < 0), the electric field is found to have northward E-z and tailward E-x components. During a positive twist (induced tail B-y > 0), the directions of E-z and E-x are reversed. The E-y component shows the expected dawn-to-dusk direction for earthward flow. The electric field components preserve their orientation across the neutral sheet, and a quasi-collinear field is observed irrespective to the tail distance. The electric field associated with the tailward flow has an opposite direction compared to the earthward flow for the negative twist. For the positive twist, the results are less clear. The corresponding plasma convection and thus the magnetic flux transport have an opposite dawn-dusk direction above and below the neutral sheet. The directions depend on the tail twist mode. The hemispherically asymmetric earthward plasma flows are suggested to be a manifestation of an asymmetric Dungey cycle in a twisted magnetotail. The role of tailward flows deserve further investigation.

  • 38.
    Denton, R. E.
    et al.
    Dartmouth Coll, Dept Phys & Astron, Hanover, NH 03755 USA..
    Sonnerup, B. U. O.
    Dartmouth Coll, Thayer Sch Engn, Hanover, NH 03755 USA..
    Russell, C. T.
    Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA..
    Hasegawa, H.
    JAXA, Inst Space & Astronaut Sci, Sagamihara, Kanagawa, Japan..
    Phan, T. -D
    Strangeway, R. J.
    Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Ergun, R. E.
    Univ Colorado, Atmospher & Space Phys Lab, Campus Box 392, Boulder, CO 80309 USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Torbert, R. B.
    Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA..
    Burch, J. L.
    Southwest Res Inst, Space Sci & Engn Div, San Antonio, TX USA..
    Vines, S. K.
    Southwest Res Inst, Space Sci & Engn Div, San Antonio, TX USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX USA.;Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD USA..
    Determining L-M-N Current Sheet Coordinates at the Magnetopause From Magnetospheric Multiscale Data2018In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 3, p. 2274-2295Article in journal (Refereed)
    Abstract [en]

    We discuss methods to determine L-M-N coordinate systems for current sheet crossings observed by the Magnetospheric Multiscale (MMS) spacecraft mission during ongoing reconnection, where e(L) is the direction of the reconnecting component of the magnetic field, B, and e(N) is normal to the magnetopause. We present and test a new hybrid method, with e(L) estimated as the maximum variance direction of B (MVAB) and e(N) as the direction of maximum directional derivative of B, and then adjust these directions to be perpendicular. In the best case, only small adjustment is needed. Results from this method, applied to an MMS crossing of the dayside magnetopause at 1305:45UT on 16 October 2015, are discussed and compared with those from other methods for which e(N) is obtained by other means. Each of the other evaluations can be combined with e(L) from MVAB in a generalized hybrid approach to provide an L-M-N system. The quality of the results is judged by eigenvalue ratios, constancy of directions using different data segments and methods, and expected sign and magnitude of the normal component of B. For this event, the hybrid method appears to produce e(N) accurate to within less than 10 degrees. We discuss variance analysis using the electric current density, J, or the J x B force, which yield promising results, and minimum Faraday residue analysis and MVAB alone, which can be useful for other events. We also briefly discuss results from our hybrid method and MVAB alone for a few other MMS reconnection events. Plain Language Summary We discuss methods for determining coordinate systems in order to study magnetic reconnection events at the magnetopause, the boundary between the ionized gas in the region of space dominated by the Earth's magnetic field and the ionized gas coming from the solar wind. We introduce a new method that combines results from multiple methods in order to determine the three coordinate directions in space. We demonstrate this method by applying it to an event observed by the Magnetospheric Multiscale spacecraft on 16 October 2015 and at other times.

  • 39. Alm, L.
    et al.
    Farrugia, C. J.
    Paulson, K. W.
    Argall, M. R.
    Torbert, R. B.
    Burch, J. L.
    Ergun, R. E.
    Russell, C. T.
    Strangeway, R. J.
    Khotyaintsev, Y. V.
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Marklund, Göran
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Giles, B. L.
    Differing Properties of Two Ion-Scale Magnetopause Flux Ropes2018In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 1, p. 114-131Article in journal (Refereed)
    Abstract [en]

    In this paper, we present results from the Magnetospheric Multiscale constellation encountering two ion-scale, magnetopause flux ropes. The two flux ropes exhibit very different properties and internal structure. In the first flux rope, there are large differences in the currents observed by different satellites, indicating variations occurring over sub-d(i) spatial scales, and time scales on the order of the ion gyroperiod. In addition, there is intense wave activity and particle energization. The interface between the two flux ropes exhibits oblique whistler wave activity. In contrast, the second flux rope is mostly quiescent, exhibiting little activity throughout the encounter. Changes in the magnetic topology and field line connectivity suggest that we are observing flux rope coalescence.

  • 40.
    Oimatsu, S.
    et al.
    Kyoto Univ, Grad Sch Sci, Kyoto, Japan..
    Nose, M.
    Kyoto Univ, Grad Sch Sci, Kyoto, Japan..
    Teramoto, M.
    Nagoya Univ, Inst Space Earth Environm Res, Nagoya, Aichi, Japan..
    Yamamoto, K.
    Kyoto Univ, Grad Sch Sci, Kyoto, Japan..
    Matsuoka, A.
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Tokyo, Japan..
    Kasahara, S.
    Univ Tokyo, Grad Sch Sci, Tokyo, Japan..
    Yokota, S.
    Osaka Univ, Grad Sch Sci, Suita, Osaka, Japan..
    Keika, K.
    Univ Tokyo, Grad Sch Sci, Tokyo, Japan..
    Le, G.
    NASA, Heliophys Sci Div, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Nomura, R.
    Japan Aerosp Explorat Agcy, Environm Test Technol Unit, Tokyo, Japan..
    Fujimoto, A.
    Kyushu Univ, Int Ctr Space Weather Sci & Educ, Fukuoka, Fukuoka, Japan..
    Sormakov, D.
    Arctic & Antarctic Res Inst, St Petersburg, Russia..
    Troshichev, O.
    Arctic & Antarctic Res Inst, St Petersburg, Russia..
    Tanaka, Y. -M
    Shinohara, M.
    Kagoshima Coll, Natl Inst Technol, Kagoshima, Japan..
    Shinohara, I.
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Tokyo, Japan..
    Miyoshi, Y.
    Nagoya Univ, Inst Space Earth Environm Res, Nagoya, Aichi, Japan..
    Slavin, J. A.
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI 48109 USA..
    Ergun, R. E.
    Univ Colorado, Dept Astrophys & Planetary Sci, Denver, CO 80202 USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Drift-Bounce Resonance Between Pc5 Pulsations and Ions at Multiple Energies in the Nightside Magnetosphere: Arase and MMS Observations2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 15, p. 7277-7286Article in journal (Refereed)
    Abstract [en]

    A Pc5 wave is observed by the Exploration of energization and Radiation in Geospace Arase satellite in the inner magnetosphere (L similar to 5.4-6.1) near postmidnight (L-magnetic local time similar to 1.8-2.5 hr) during the storm recovery phase on 27 March 2017. Its azimuthal wave number (m-number) is estimated using two independent methods with satellites and ground observations to be -8 to -15. The direct measurement of the m-number enables us to calculate the resonance energy. The flux oscillations of H+ and O+ ions at >= 56.3 keV are caused by drift resonance and those of O+ ions at <= 18.6 keV by bounce resonance. Resonances of O+ ions at multiple energies are simultaneously observed for the first time. The enhancement of the O+/H+ flux ratio at <= 18.6 keV indicates selective acceleration of O+ ions through bounce resonance. Plain Language Summary Geomagnetic pulsations are magnetic fluctuations excited by solar wind or plasma instabilities in the magnetosphere. Pc5 waves are continuous geomagnetic pulsations with a period of 150-600 s. A Pc5 wave was observed in the inner magnetosphere during a magnetic storm on 27 March 2017. It propagated westward with a wave number of 8 to 15 and resonated with charged particles, resulting in oscillations of the H+ and O+ ion fluxes at >= 56.3 keV and the O+ ion fluxes at <= 18.6 keV. Resonances of O+ ions at multiple energies are simultaneously observed for the first time. At the same time, the O+/H+ flux ratio at <= 18.6 keV enhanced corresponding to the O+ ion flux oscillations, which indicates selective acceleration of O+ ions through resonances.

  • 41.
    Belyayev, Serhiy
    et al.
    KTH. Lviv Center of Institute of Space Research, NASU/SSAU, Ukraine.
    Ivchenko, Nickolay
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Effect of second harmonic in pulse-width-modulation-based DAC for feedback of digital fluxgate magnetometer2018In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 29, no 4, article id 045008Article in journal (Refereed)
    Abstract [en]

    Digital fluxgate magnetometers employ processing of the measured pickup signal to produce the value of the compensation current. Using pulse-width modulation with filtering for digital to analog conversion is a convenient approach, but it can introduce an intrinsic source of nonlinearity, which we discuss in this design note. A code shift of one least significant bit changes the second harmonic content of the pulse train, which feeds into the pick-up signal chain despite the heavy filtering. This effect produces a code-dependent nonlinearity. This nonlinearity can be overcome by the specific design of the timing of the pulse train signal. The second harmonic is suppressed if the first and third quarters of the excitation period pulse train are repeated in the second and fourth quarters. We demonstrate this principle on a digital magnetometer, achieving a magnetometer noise level corresponding to that of the sensor itself. 

  • 42.
    Hajihoseini, H.
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Science Institute, University of Iceland, Dunhaga 3, IS-107, Reykjavik, Iceland.
    Kateb, M.
    Ingvarsson, S.
    Gudmundsson, J. T.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Science Institute, University of Iceland, Dunhaga 3, IS-107, Reykjavik, Iceland.
    Effect of substrate bias on properties of HiPIMS deposited vanadium nitride films2018In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 663, p. 126-130Article in journal (Refereed)
    Abstract [en]

    We report on the effect of varying the substrate bias on the morphology, composition, structural, and electrical properties of vanadium nitride films deposited by high power impulse magnetron sputtering (HiPIMS). The optimum substrate bias is found to be −50 V, which gives the highest film density, the lowest electrical resistivity, and the lowest surface roughness at the highest deposition rate. We demonstrate how increasing the substrate bias voltage leads to a highly textured film. The preferred orientation of the film changes from (111) to (200) as the substrate bias voltage is increased. An X-ray pole scan shows that the (111) plane grows parallel to the SiO2 substrate when the substrate is grounded while it is gradually replaced by the (200) plane as the substrate bias voltage is increased up to −200 V. The lowest electrical resistivity is measured as 48.4 μΩ cm for the VN film deposited under substrate bias of −50 V. This is among the lowest room temperature values that have been reported for a VN film. We found that the nitrogen concentration presents a decline by 6.5 percentage points as the substrate bias is changed from ground to −200 V. 

  • 43. Chen, L. -J
    et al.
    Wang, S.
    Wilson, L. B. , I I I
    Schwartz, S.
    Bessho, N.
    Moore, T.
    Gershman, D.
    Giles, B.
    Malaspina, D.
    Wilder, F. D.
    Ergun, R. E.
    Hesse, M.
    Lai, H.
    Russell, C.
    Strangeway, R.
    Torbert, R. B.
    Vinas, F. -A
    Burch, J.
    Lee, S.
    Pollock, C.
    Dorelli, J.
    Paterson, W.
    Ahmadi, N.
    Goodrich, K.
    Lavraud, B.
    Le Contel, O.
    Khotyaintsev, Yu.V.
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Boardsen, S.
    Wei, H.
    Le, A.
    Avanov, L.
    Electron Bulk Acceleration and Thermalization at Earth's Quasiperpendicular Bow Shock2018In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 120, no 22, article id 225101Article in journal (Refereed)
    Abstract [en]

    Electron heating at Earth's quasiperpendicular bow shock has been surmised to be due to the combined effects of a quasistatic electric potential and scattering through wave-particle interaction. Here we report the observation of electron distribution functions indicating a new electron heating process occurring at the leading edge of the shock front. Incident solar wind electrons are accelerated parallel to the magnetic field toward downstream, reaching an electron-ion relative drift speed exceeding the electron thermal speed. The bulk acceleration is associated with an electric field pulse embedded in a whistler-mode wave. The high electron-ion relative drift is relaxed primarily through a nonlinear current-driven instability. The relaxed distributions contain a beam traveling toward the shock as a remnant of the accelerated electrons. Similar distribution functions prevail throughout the shock transition layer, suggesting that the observed acceleration and thermalization is essential to the cross-shock electron heating. © 2018 American Physical Society.

  • 44. Argall, M. R.
    et al.
    Paulson, K.
    Alm, L.
    Rager, A.
    Dorelli, J.
    Shuster, J.
    Wang, S.
    Torbert, R. B.
    Vaith, H.
    Dors, I.
    Chutter, M.
    Farrugia, C.
    Burch, J.
    Pollock, C.
    Giles, B.
    Gershman, D.
    Lavraud, B.
    Russell, C. T.
    Strangeway, R.
    Magnes, W.
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Khotyaintsev, Yu. V.
    Ergun, R. E.
    Ahmadi, N.
    Electron Dynamics Within the Electron Diffusion Region of Asymmetric Reconnection2018In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 1, p. 146-162Article in journal (Refereed)
    Abstract [en]

    We investigate the agyrotropic nature of electron distribution functions and their substructure to illuminate electron dynamics in a previously reported electron diffusion region (EDR) event. In particular, agyrotropy is examined as a function of energy to reveal detailed finite Larmor radius effects for the first time. It is shown that the previously reported approximate to 66eV agyrotropic "crescent" population that has been accelerated as a result of reconnection is evanescent in nature because it mixes with a denser, gyrotopic background. Meanwhile, accelerated agyrotropic populations at 250 and 500eV are more prominent because the background plasma at those energies is more tenuous. Agyrotropy at 250 and 500eV is also more persistent than at 66eV because of finite Larmor radius effects; agyrotropy is observed 2.5 ion inertial lengths from the EDR at 500eV, but only in close proximity to the EDR at 66eV. We also observe linearly polarized electrostatic waves leading up to and within the EDR. They have wave normal angles near 90 degrees, and their occurrence and intensity correlate with agyrotropy. Within the EDR, they modulate the flux of 500eV electrons travelling along the current layer. The net electric field intensifies the reconnection current, resulting in a flow of energy from the fields into the plasma. Plain Language Summary The process of reconnection involves an explosive transfer of magnetic energy into particle energy. When energetic particles contact modern technology such as satellites, cell phones, or other electronic devices, they can cause random errors and failures. Exactly how particles are energized via reconnection, however, is still unknown. Fortunately, the Magnetospheric Multiscale mission is finally able to detect and analyze reconnection processes. One recent finding is that energized particles take on a crescent-shaped configuration in the vicinity of reconnection and that this crescent shape is related to the energy conversion process. In our paper, we explain why the crescent shape has not been observed until now and inspect particle motions to determine what impact it has on energy conversion. When reconnection heats the plasma, the crescent shape forms from the cool, tenuous particles. As plasmas from different regions mix, dense, nonheated plasma obscures the crescent shape in our observations. The highest-energy particle population created by reconnection, though, also contains features of the crescent shape that are more persistent but appear less dramatically in the data.

  • 45.
    Eriksson, Elin
    et al.
    Swedish Inst Space Phys, Uppsala, Sweden.;Uppsala Univ, Dept Phys & Astron, Uppsala, Sweden..
    Vaivads, Andris
    Swedish Inst Space Phys, Uppsala, Sweden..
    Graham, Daniel B.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Divin, Andrey
    Swedish Inst Space Phys, Uppsala, Sweden.;St Petersburg State Univ, Dept Phys, St Petersburg, Russia..
    Khotyaintsev, Yuri V.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Yordanova, Emiliya
    Swedish Inst Space Phys, Uppsala, Sweden..
    Andre, Mats
    Swedish Inst Space Phys, Uppsala, Sweden..
    Giles, Barbara L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Pollock, Craig J.
    Denali Sci LLC, Healy, AK USA..
    Russell, Christopher T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Le Contel, Olivier
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Ecole Polytech,CNRS,Lab Phys Plasmas, Paris, France..
    Torbert, Roy B.
    Univ New Hampshire, Dept Phys, Durham, NH 03824 USA..
    Ergun, Robert E.
    Univ Colorado, Atmospher & Space Phys Lab, Campus Box 392, Boulder, CO 80309 USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Burch, James L.
    Southwest Res Inst, San Antonio, TX USA..
    Electron Energization at a Reconnecting Magnetosheath Current Sheet2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 16, p. 8081-8090Article in journal (Refereed)
    Abstract [en]

    We present observations of electron energization within a sub-ion-scale magnetosheath current sheet (CS). A number of signatures indicate ongoing reconnection, including the thickness of the CS (similar to 0.7 ion inertial length), nonzero normal magnetic field, Hall magnetic fields with electrons carrying the Hall currents, and electron heating. We observe localized electron acceleration and heating parallel to the magnetic field at the edges of the CS. Electrostatic waves observed in these regions have low phase velocity and small wave potentials and thus cannot provide the observed acceleration and heating. Instead, we find that the electrons are accelerated by a parallel potential within the separatrix regions. Similar acceleration has been reported based on magnetopause and magnetotail observations. Thus, despite the different plasma conditions in magnetosheath, magnetopause, and magnetotail, the acceleration mechanism and corresponding heating of electrons is similar. Plain Language Summary Magnetic reconnection is an important physical energy conversion process in astrophysical and laboratory plasmas. The easiest place to analyze magnetic reconnection is in near-Earth space. Due to lack of sufficient electron resolution of previous spacecraft missions, there are many unanswered questions regarding electron heating and acceleration processes at small scales. In particular, the regime where thermal pressure dominates over magnetic pressure, the most common state of plasmas in the Universe, is little explored. In this letter we study such a regime using the four-spacecraft Magnetospheric Multiscale mission. We analyze a reconnecting current sheet in the magnetosheath. We show that electrons are energized by a parallel potential, similar to what has been observed in the different plasma regimes the magnetopause and magnetotail. Thus, despite different plasma conditions, a similar acceleration mechanism and corresponding heating of electrons is occurring in all these regions.

  • 46. Liu, C. M.
    et al.
    Fu, H. S.
    Vaivads, A.
    Khotyaintsev, Y. V.
    Gershman, D. J.
    Hwang, K-J
    Chen, Z. Z.
    Cao, D.
    Xu, Y.
    Yang, J.
    Peng, F. Z.
    Huang, S. Y.
    Burch, J. L.
    Giles, B. L.
    Ergun, R. E.
    Russell, C. T.
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Le Contel, O.
    Electron Jet Detected by MMS at Dipolarization Front2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 2, p. 556-564Article in journal (Refereed)
    Abstract [en]

    Using MMS high-resolution measurements, we present the first observation of fast electron jet (V-e similar to 2,000 km/s) at a dipolarization front (DF) in the magnetotail plasma sheet. This jet, with scale comparable to the DF thickness (similar to 0.9 d(i)), is primarily in the tangential plane to the DF current sheet and mainly undergoes the E x B drift motion; it contributes significantly to the current system at the DF, including a localized ring-current that can modify the DF topology. Associated with this fast jet, we observed a persistent normal electric field, strong lower hybrid drift waves, and strong energy conversion at the DF. Such strong energy conversion is primarily attributed to the electron-jet-driven current (E.j(e) approximate to 2 E.j(i)), rather than the ion current suggested in previous studies.

  • 47.
    Phan, T. D.
    et al.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Eastwood, J. P.
    Imperial Coll London, Blackett Lab, London, England..
    Shay, M. A.
    Univ Delaware, Newark, DE USA..
    Drake, J. F.
    Univ Maryland, College Pk, MD 20742 USA..
    Sonnerup, B. U. O.
    Dartmouth Coll, Hanover, NH 03755 USA..
    Fujimoto, M.
    JAXA, ISAS, Sagamihara, Kanagawa, Japan..
    Cassak, P. A.
    West Virginia Univ, Morgantown, WV USA..
    Oieroset, M.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Torbert, R. B.
    Univ New Hampshire, Durham, NH 03824 USA..
    Rager, A. C.
    Catholic Univ Amer, Washington, DC 20064 USA.;NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Dorelli, J. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Pollock, C.
    Denali Sci, Healy, AK USA..
    Pyakurel, P. S.
    Univ Delaware, Newark, DE USA..
    Haggerty, C. C.
    Univ Delaware, Newark, DE USA..
    Khotyaintsev, Y.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Planetol, Toulouse, France..
    Saito, Y.
    JAXA, ISAS, Sagamihara, Kanagawa, Japan..
    Oka, M.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Ergun, R. E.
    Univ Colorado, LASP, Boulder, CO 80309 USA..
    Retino, A.
    Ecole Polytech, CNRS, Paris, France..
    Le Contel, O.
    Ecole Polytech, CNRS, Paris, France..
    Argall, M. R.
    Univ New Hampshire, Durham, NH 03824 USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Moore, T. E.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Wilder, F. D.
    Univ Colorado, LASP, Boulder, CO 80309 USA..
    Strangeway, R. J.
    Univ Calif Los Angeles, Los Angeles, CA USA..
    Russell, C. T.
    Univ Calif Los Angeles, Los Angeles, CA USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Magnes, W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Electron magnetic reconnection without ion coupling in Earth's turbulent magnetosheath2018In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 557, no 7704, p. 202-+Article in journal (Refereed)
    Abstract [en]

    Magnetic reconnection in current sheets is a magnetic-to-particle energy conversion process that is fundamental to many space and laboratory plasma systems. In the standard model of reconnection, this process occurs in a minuscule electron-scale diffusion region(1,2). On larger scales, ions couple to the newly reconnected magnetic-field lines and are ejected away from the diffusion region in the form of bi-directional ion jets at the ion Alfven speed(3-5). Much of the energy conversion occurs in spatially extended ion exhausts downstream of the diffusion region(6). In turbulent plasmas, which contain a large number of small-scale current sheets, reconnection has long been suggested to have a major role in the dissipation of turbulent energy at kinetic scales(7-11). However, evidence for reconnection plasma jetting in small-scale turbulent plasmas has so far been lacking. Here we report observations made in Earth's turbulent magnetosheath region (downstream of the bow shock) of an electron-scale current sheet in which diverging bi-directional super-ion-Alfvenic electron jets, parallel electric fields and enhanced magnetic-to-particle energy conversion were detected. Contrary to the standard model of reconnection, the thin reconnecting current sheet was not embedded in a wider ion-scale current layer and no ion jets were detected. Observations of this and other similar, but unidirectional, electron jet events without signatures of ion reconnection reveal a form of reconnection that can drive turbulent energy transfer and dissipation in electron-scale current sheets without ion coupling.

  • 48.
    Norgren, C.
    et al.
    Univ Bergen, Birkeland Ctr Space Sci, Dept Phys & Technol, Bergen, Norway.;Swedish Inst Space Phys, Uppsala, Sweden..
    Graham, D. B.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Khotyaintsev, Yu, V
    Swedish Inst Space Phys, Uppsala, Sweden..
    Andre, M.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Vaivads, A.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Hesse, M.
    Univ Bergen, Birkeland Ctr Space Sci, Dept Phys & Technol, Bergen, Norway..
    Eriksson, E.
    Swedish Inst Space Phys, Uppsala, Sweden.;Uppsala Univ, Dept Phys & Astron, Uppsala, Sweden..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Planetol, CNES, UPS,CNRS, Toulouse, France..
    Burch, J.
    Southwest Res Inst, San Antonio, TX USA..
    Fuselier, S.
    Southwest Res Inst, San Antonio, TX USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX USA..
    Magnes, W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Gershman, D. J.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA.;NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90024 USA..
    Electron Reconnection in the Magnetopause Current Layer2018In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 11, p. 9222-9238Article in journal (Refereed)
    Abstract [en]

    The electron dynamics within thin current sheets plays a key role both for the process of magnetic reconnection and other energy transfer mechanisms but, from an observational point of view, is not well understood. In this paper we report observations of a reconnecting current sheet with intermediate guide field B-G = 0.5B(in), where B-in is the magnetic field amplitude in the inflow regions. The current sheet width is comparable to electron spatial scales. It shows a bifurcated structure and is embedded within the magnetopause current layer with thickness of several ion scales. The electron scale current sheet has strong out-of-plane and in-plane currents, Hall electric and magnetic fields, a finite magnetic field component normal to the current sheet, and nongyrotropic electron distributions formed due to finite gyroradius effects at the boundary of the current sheet. Comparison between test particle simulations and electron data shows that electrons approaching from the edge of the largest magnetic curvature are scattered to perpendicular pitch angles in the center of the current sheet while electrons entering from the opposite side remain close to field aligned. The comparison also shows that an observed depletion in phase space at antiparallel pitch angles can be explained if an out-of-plane electric field, which due to the guide field is close to antiparallel to the magnetic field, is present in the center of the current sheet. This electric field would be consistent with the reconnection electric field, and we therefore interpret the depletion of electron phase space density as a manifestation of ongoing reconnection.

  • 49.
    Vignitchouk, Ladislas
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Delzanno, G. L.
    Los Alamos Natl Lab, Theoret Div, Los Alamos, NM 87545 USA..
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Electron reflection effects on particle and heat fluxes to positively charged dust subject to strong electron emission2018In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 25, no 6, article id 063702Article in journal (Refereed)
    Abstract [en]

    A new model describing dust charging and heating in unmagnetized plasmas in the presence of large electron emission currents is presented. By accounting for the formation of a potential well due to trapped emitted electrons when the dust is positively charged, this model extends the so-called OML+ approach, thus far limited to thermionic emission, by including electron-induced emission processes, and in particular low-energy quasi-elastic electron reflection. Revised semi-analytical formulas for the current and heat fluxes associated with emitted electrons are successfully validated against particle-in-cell simulations and predict an overall reduction of dust heating by up to a factor of 2. When applied to tungsten dust heating in divertor-like plasmas, the new model predicts that the dust lifetime increases by up to 80%, as compared with standard orbital-motion-limited estimates.

  • 50.
    Torbert, R. B.
    et al.
    Univ New Hampshire, Durham, NH 03824 USA.;Southwest Res Inst SwRI, San Antonio, TX 78228 USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Saito, Y.
    et al,