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  • 301.
    Eriksson, Tommy
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Resonant Waves in the Terrestrial Magnetosphere2005Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Waves in the mHz frequency range are a prominent feature in the terrestrial magnetosphere. In this frequency range the waves have wavelengths comparable to the lengths of the geomagnetic field lines. The waves are then standing waves along closed field lines with endpoints in the southern and northern ionosphere. Waves play an important role in the distribution of energy in the magnetosphere and mHz waves can accelerate electrons to MeV energies and have been proposed as a driver of auroral arcs. They can also be used as a diagnostic tool for determining the plasma density. There are two important classes of these low frequency waves. One has large azimuthal wavelength and is usually associated with driving mechanisms outside the magnetosphere, such as the Kelvin-Helmholtz instability at the magnetopause. The other has small azimuthal wavelength and is associated with plasma instabilities inside the magnetosphere. Both types of waves are studied in this thesis with an emphasis on the small azimuthal wavelength waves. For the type of wave with large azimuthal wavelength there is however, a considerable debate about the driving mechanism. One recently suggested driver is coherent magnetohydrodynamic waves in the solar wind. Part of this thesis studies this experimentally and we conclude that, at least on some occasions, this driving mechanism come into play. The Cluster satellites are used to study the morphology of the waves. We demonstrate the ability of Cluster to determine the azimuthal wave number of the waves and also how the structure along the magnetic field lines can be determined. This gives information regarding the harmonic number of the standing waves, which in turn says something about the driver of the waves. We also look at possible excitation mechanisms for the small azimuthal wavelength waves.

  • 302.
    Eriksson, Tommy
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Wave pulsations in the magnetosphere and their dependence on the solar wind2003Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 303.
    Eriksson, Tommy
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Blomberg, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Glassmeier, K.-H.
    Institute for Geophysics and Extraterrestrial Physics, Technical University of Braunschweig, Tyskland.
    Cluster satellite observations of mHz pulsations in the dayside magnetosphere2006Ingår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 38, nr 8, s. 1730-1737Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    On 17 August 2002 the Cluster spacecraft moved through the dayside magnetosphere. Between 16:00 and 18:30 LIT clear monochromatic oscillations are seen in both electric field and magnetometer data. The frequency is 4.2 mHz in the spacecraft frame of reference. The oscillations have a clear spatial localisation. The magnetic field oscillations are radially polarised in the plane perpendicular to the background magnetic field, indicating that the wave is in the poloidal mode. From the difference in phase between the satellites we estimate the azimuthal wave number, in, to be about 130, consistent with the magnetic field polarisation. The frequency is stable for different L-values as well as over time. From the value of in, the Doppler shift due to satellite motion is estimated to 0.5 mHz. By looking at the phase of the electric and the magnetic field close to the equator we conclude that the oscillations are in a mode with an odd number of half wavelengths between the two ionospheres.

  • 304.
    Eriksson, Tommy
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Blomberg, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Schaefer, S.
    Institute for Geophysics and Extraterrestrial Physics, Technical University of Braunschweig, Germany.
    Glassmeier, K.-H.
    Institute for Geophysics and Extraterrestrial Physics, Technical University of Braunschweig, Germany.
    On the excitation of ULF waves by solar wind pressure enhancements2006Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 24, nr 11, s. 3161-3172Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the onset and development of an ultra low frequency (ULF) pulsation excited by a storm sudden commencement. On 30 August 2001, 14: 10 UT, the Cluster spacecraft are located in the dayside magnetosphere and observe the excitation of a ULF pulsation by a threefold enhancement in the solar wind dynamic pressure. Two different harmonics are observed by Cluster, one at 6.8 mHz and another at 27 mHz. We observe a compressional wave and the development of a toroidal and poloidal standing wave mode. The toroidal mode is observed over a narrow range of L-shells whereas the poloidal mode is observed to have a much larger radial extent. By looking at the phase difference between the electric and magnetic fields we see that for the first two wave periods both the poloidal and toroidal mode are travelling waves and then suddenly change into standing waves. We estimate the azimuthal wave number for the 6.8 mHz to be m = 10 +/- 3. For the 27 mHz wave, m seems to be several times larger and we discuss the implications of this. We conclude that the enhancement in solar wind pressure excites eigenmodes of the geomagnetic cavity/waveguide that propagate tailward and that these eigenmodes in turn couple to toroidal and poloidal mode waves. Thus our observations give firm support to the magnetospheric waveguide theory.

  • 305.
    Eriksson, Tommy
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Blomberg, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Schaefer, S.
    Institute for Geophysics and Extraterrestrial Physics, Technical University of Braunschweig, Germany.
    Glassmeier, K.-H.
    Institute for Geophysics and Extraterrestrial Physics, Technical University of Braunschweig, Germany.
    Sunward propagating Pc5 waves observed on the post-midnight magnetospheric flank2008Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 26, nr 6, s. 1567-1579Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The overall focus on the driver of toroidal Pc5 waves has been on processes located at or acting on the dayside magnetopause and dayside flanks of the magnetosphere. These processes can generate waves that propagate tailward in the magnetosphere. However, an increasing number of studies, both theoretical and experimental, have looked at waves propagating sunward and that are caused by processes in the magnetotail. Here we present an ultra low frequency (ULF) wave observed in the post-midnight/morning sector of the magnetosphere at L=16 R-E. The wave has a toroidal mode polarization. We estimate the azimuthal wave number to m=3, consistent with a toroidal mode type pulsation. The positive sign indicates that the wave is propagating sunward and this is confirmed by looking at the Poynting flux of the wave. The frequency of the wave is not constant with time but shows a small increase in the beginning of the event up to over 2.0 mHz. Then the frequency decreases to 1.0 mHz. This decrease coincides with a drop in the total magnetic field strength and we speculate if this is related to an observed reversal of the sign of the interplanetary magnetic field (IMF) By-component. This event occurs during relatively quiet magnetospheric conditions with a solar wind speed of approximately 400 km/s. Thus this event is highly likely to be driven by a source in the magnetotail and the change in frequency is an excellent example that the frequency of an ULF wave may be modulated by changes of the plasma parameters on the resonant field line.

  • 306.
    Eriksson, Tommy
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Blomberg, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Walker, A. D. M.
    School of Pure and Applied Physics, University of KwaZulu-Natal, Durban, South Africa.
    Glassmeier, K.-H.
    Institute for Geophysics and Extraterrestrial Physics, Technical University of Braunschweig, Germany.
    Poloidal ULF oscillations in the dayside magnetosphere: a Cluster study2005Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 23, nr 7, s. 2679-2686Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three ULF wave events, all occurring in the dayside magnetopshere during magnetically quiet times, are studied using the Cluster satellites. The multi-point measurements obtained from Cluster are used to determine the azimuthal wave number for the events by means of the phase shift and the azimuthal separation between the satellites. Also, the polarisation of the electric and magnetic fields is examined in a field-aligned coordinate system, which, in turn, gives the mode of the oscillations. The large-inclination orbits of Cluster allow us to examine the phase relationship between the electric and magnetic fields along the field lines. The events studied have large azimuthal wave numbers (m similar to 100), two of them have eastward propagation and all are in the poloidal mode, consistent with the large wave numbers. We also use particle data from geosynchronous satellites to look for signatures of proton injections, but none of the events show any sign of enhanced proton flux. Thus, the drift-bounce resonance instability seems unlikely to have played any part in the excitation of these pulsations. As for the drift-mirror instability we conclude that it would require an unreasonably high plasma pressure for the instability criterion to be satisfied.

  • 307.
    Eriksson, Tommy
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Walker, A. D. M.
    School of Pure and Applied Physics, University of KwaZulu-Natal, Durban, South Africa.
    Stephenson, J. A. E.
    School of Pure and Applied Physics, University of KwaZulu-Natal, Durban, South Africa.
    A statistical correlation of Pc5 pulsations and solar wind pressure oscillations2006Ingår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 38, nr 8, s. 1763-1771Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The SHARE high frequency (HF) radar in Antarctica is used to compare ionospheric plasma flow oscillations in the Pc5 frequency range with low-frequency oscillations in the solar wind pressure measured by the ACE spacecraft. Ten different days in 2000 and 2001 are analysed with respect to different frequencies and geomagnetic latitudes. Both data sets are bandpass filtered and a complex demodulation technique is used to calculate the correlation in each band. On a number of occasions the wave packet structure of the Pc5 pulsations is in good or excellent agreement with the wave packet structure of the solar wind pressure oscillations. This strongly suggests that the oscillations were directly driven by the solar wind. Particularly good correlation is found in the frequency band 0.8-1.2 mHz. Pulsations in this frequency range are hard to reconcile with the magnetospheric cavity mode model. We conclude that, at least on some occasions, Pc5 pulsations may be directly driven and the magnetosphere cavity/waveguide then assumes a more passive role.

  • 308. Erlandson, R. E.
    et al.
    Zanetti, L. J.
    Acuna, M. H.
    Eriksson, A. I.
    Eliasson, L.
    Boehm, M. H.
    Blomberg, Lars
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Freja observations of electromagnetic ion cyclotron ELF waves and transverse oxygen ion acceleration on auroral field lines1994Ingår i: Geophysical Research Letters, ISSN 00948276 (ISSN), Vol. 21, nr 17, s. 1855-1858Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Extremely low-frequency (ELF) magnetic and electric field plasma wave emissions were recorded on 2 October 1993 on auroral field lines by the Magnetic Field Experiment during Freja orbit 4770. The ELF wave frequencies were below the local oxygen gyrofrequency (25 Hz) and between the helium and proton gyrofrequencies (100 to 400 Hz). The ELF waves, interpreted as electromagnetic ion cyclotron (EMIC) waves, were observed in a region of inverted-v-type electron precipitation. The EMIC waves were correlated over time with auroral and lower energy (≈ 100 eV) electrons, which are both possible sources of free energy, and also with transversely accelerated oxygen ions. The waves above the helium gyrofrequency were more closely correlated with the transverse oxygen ion acceleration than the waves below the oxygen gyrofrequency. These observations are consistent with a scenario in which electron beams generate EMIC waves, which then produce transverse oxygen ion acceleration through a gyroresonant interaction.

  • 309.
    Ersmark, Tore
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Geant4 Monte Carlo Simulations of the International Space Station Radiation Environment2006Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    A detailed characterization of the proton and neutron induced radiation environment onboard Columbus and the International Space Station (ISS) has been carried out using the Geant4 Monte Carlo particle transport toolkit. Dose and dose equivalent rates, as well as penetrating particle spectra corresponding to incident trapped protons, GCR protons, SPE protons and cosmic ray albedo neutrons are presented.

    These results are based on detailed Geant4 geometry models of Columbus and ISS, comprising a total of about 750 and 350 geometry volumes, respectively. Additionally, the physics models of Geant4 have been validated with respect to space radiation shielding applications. Geant4 physics configurations based on the “Binary Cascade” and “Bertini Cascade” models of hadronic reactions were found to adequately model the particle interactions of the relevant space radiation fields. Other studied Geant4 models of hadronic reactions were found to be unsatisfactory for this application.

    Calculated trapped proton dose rates are found to be strongly dependent on ISS altitude. Dose rates for different locations inside the Columbus cabin are presented, as well as for different models of the incident space radiation flux. Dose rates resulting from incident anisotropic trapped protons are found to be lower, or equal to, those of omnidirectional models. The anisotropy induced by the asymmetric shielding distribution of Columbus/ISS is also studied. GCR proton dose rates are presented, and it is demonstrated that the presence of thick shielding may increase the dose rate. A possible problem using Geant4 for future studies of effects induced by high-energy GCR ions is discussed. The dose rate due to cosmic ray albedo neutrons is demonstrated to be negligible.

    The calculated trapped proton dose rates are 120 μGy/d and 79 μGy/d for solar minimum and maximum conditions, respectively. GCR dose rates are estimated based on calculated GCR proton dose rates to 161 μGy/d and 114 μGy/d, respectively. These dose rates are found to be compatible with experimental measurements.

  • 310.
    Fahleson, Ulf
    KTH, Tidigare Institutioner.
    Results from Magnetospheric Electric Field Observations1979Rapport (Övrigt vetenskapligt)
  • 311.
    Fahleson, Ulf
    KTH, Tidigare Institutioner.
    Sailing on the solar wind1972Rapport (Övrigt vetenskapligt)
  • 312.
    Fahleson, Ulf
    KTH, Tidigare Institutioner.
    Upstream Wakes in Magnetohydrodynamic Flow1967Rapport (Övrigt vetenskapligt)
  • 313.
    Fahleson, Ulf
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Fälthammar, Carl-Gunne
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Pedersen, Arne
    Ionospheric temperature and density measurements by means of spherical double probes1974Ingår i: Planetary and Space Science, ISSN 00320633, Vol. 22, s. 41-66Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rocket-borne double probes for electric field measurements can be intermittently operated in special, diagnostic modes involving current bias and low-impedance shunts to obtain information on the properties of the ambient ionospheric plasma along the flight path. Several such modes, and the information that they can provide, are analyzed. For example, in a low-impedance mode with asymmetric bias, the attenuation ratio (i.e. signal amplitude in this mode over the signal amplitude in the electric-field measuring mode) is in a simple way related to the electron temperature of the ambient plasma. The special surface coatings (Aquadag or vitreous carbon) normally used for electric field probes provide very homogeneous surface properties, a feature which also contributes to the reliability of the electron temperature measurements. In addition to electron temperature, the modes analyzed can be used to measure electron density and to give some information on ion temperature. The data from four rocket flights from ESRANGE are discussed in the light of these results. Electron temperature was measured in three of these flights. In all cases the temperature profile is in good agreement with theoretically predicted profiles based on the CIRA 1965 reference atmosphere and the solar illumination prevailing during the respective flights (twilight). Electron density profiles obtained by means of the double probe are in good agreement with the density measured by the Langmuir probe in the two flights for which both kinds of data are available. They are also in agreement with the electron density data available from ionosondes. Finally, pulses occurring when one of the probes passed through the rocket’s shadow, are used to determine the photoelectron yield of the probe coatings (Aquadag or vitreous carbon). The values obtained, (7 ± 3) × 10-6 A/m2 for Aquadag and (4 ± 2) × 10-6 A/m2 for vitreous carbon are in good agreement with expectations based on laboratory data and solar Lyman α radiation. © 1974.

  • 314.
    Falck, Simon
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Urbana och regionala studier.
    Snickars, Folke
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Urbana och regionala studier.
    EISCAT in Space: Spatial aspects of the economic and societal importance of the European incoherent scatter radar system and an ionospheric heater in Fenno-Scandinavia and on Svalbard2014Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Over the last three decades, the European Incoherent Scatter Scientific Association (EISCAT) has provided the scientific community with outstanding high-latitude data for research on the lower, middle and upper atmosphere and ionosphere using the incoherent scatter radar technique. The research facilities are located north of the Arctic Circle in Finland, Norway, Sweden and on Svalbard, and have since they first were taken into operation in August 1981 contributed a remarkable scientific output. This research has contributed to the understanding of different space and atmospheric phenomena and opened up and to several new fields of research. EISCAT is currently planning the next generation research facility, EISCAT_3D, which is an projected investment of more than 1,1 billion SEK (135 million €) with planned start of construction in 2015, first operations in 2018, and to be in full operation 2021. EISCAT_3D is anticipated to provide researchers with opportunities to conduct novel scientific experiments that may shift the frontiers in several scientific disciplines, but may also be utilized to develop services with specific societal values, see Kero et al. (2013). 

    This study examines the economic and societal importance of EISCAT in a spatial context. The results indicate that EISCAT generates minor purely economic effects but contributes to strengthening the regional competitiveness and attractiveness, mainly though a remarkable scientific output and extra-regional linkages which enable continual renewal and dynamism of local knowledge. EISCAT has also implied a large injection of research funding to the region. It is argued ESICAT should not only be considered as a research facility with great scientific value but also as an interconnecting infrastructure and organisation in value creating knowledge networks with global reach. The study suggests that EISCAT_3D is an investment with many important potential implications but that the related development work needs to carefully consider how to promote a high level of absorptive capacity among organisations with related activities. It is obvious that a proactive work and cooperation with national, regional and local actors will impact a full range of benefits from EISCAT_3D.

  • 315. Farrugia, C. J.
    et al.
    Lugaz, N.
    Alm, L.
    Vasquez, B.
    Argall, M. R.
    Kucharek, H.
    Matsui, H.
    Torbert, R. B.
    Lavraud, B.
    Le Contel, O.
    Cohen, I. J.
    Burch, J. L.
    Russell, C. T.
    Strangeway, R. J.
    Shuster, J.
    Dorelli, J. C.
    Eastwood, J. P.
    Ergun, R. E.
    Fuselier, S. A.
    Gershman, D. J.
    Giles, B. L.
    Khotyaintsev, Y. V.
    Lindqvist, Per-Arne
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marklund, Göran
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Paulson, K. W.
    Petrinec, S. M.
    Phan, T. D.
    Pollock, C. J.
    MMS Observations of Reconnection at Dayside Magnetopause Crossings During Transitions of the Solar Wind to Sub-Alfvénic Flow2017Ingår i: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, nr 10, s. 9934-9951Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present MMS observations during two dayside magnetopause crossings under hitherto unexamined conditions: (i) when the bow shock is weakening and the solar wind transitioning to sub-Alfvénic flow and (ii) when it is reforming. Interplanetary conditions consist of a magnetic cloud with (i) a strong B (∼20 nT) pointing south and (ii) a density profile with episodic decreases to values of ∼0.3 cm−3 followed by moderate recovery. During the crossings the magnetosheath magnetic field is stronger than the magnetosphere field by a factor of ∼2.2. As a result, during the outbound crossing through the ion diffusion region, MMS observed an inversion of the relative positions of the X and stagnation (S) lines from that typically the case: the S line was closer to the magnetosheath side. The S line appears in the form of a slow expansion fan near which most of the energy dissipation is taking place. While in the magnetosphere between the crossings, MMS observed strong field and flow perturbations, which we argue to be due to kinetic Alfvén waves. During the reconnection interval, whistler mode waves generated by an electron temperature anisotropy (Te⊥>Te∥) were observed. Another aim of the paper is to distinguish bow shock-induced field and flow perturbations from reconnection-related signatures. The high-resolution MMS data together with 2-D hybrid simulations of bow shock dynamics helped us to distinguish between the two sources. We show examples of bow shock-related effects (such as heating) and reconnection effects such as accelerated flows satisfying the Walén relation.

  • 316.
    Fazinic, Stjepko
    et al.
    Rudjer Boskovic Inst, Bijenicka 54, Zagreb 10000, Croatia..
    Tadic, Tonic
    Rudjer Boskovic Inst, Bijenicka 54, Zagreb 10000, Croatia..
    Vuksic, Marin
    Rudjer Boskovic Inst, Bijenicka 54, Zagreb 10000, Croatia..
    Rubel, Marek
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Petersson, Per
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Fortuna-Zalesna, Elibieta
    Warsaw Univ Technol, Fac Mat Sci & Technol, Woloska 141, PL-02507 Warsaw, Poland..
    Widdowson, Anna
    Culham Sci Ctr, Culham Ctr Fus Energy, Abingdon OX14 3DB, Oxon, England..
    Ion Microbeam Analyses of Dust Particles and Codeposits from JET with the ITER-Like Wall2018Ingår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 90, nr 9, s. 5744-5752Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Generation of metal dust in the JET tokamak with the ITER-like wall (ILW) is a topic of vital interest to next-step fusion devices because of safety issues with plasma operation. Simultaneous Nuclear Reaction Analysis (NRA) and Particle Induced X-ray Emission (PIXE) with a focused four MeV He-3 microbeam was used to determine the composition of dust particles related to the JET operation with the ILW. The focus was on "Be-rich particles" collected from the deposition zone on the inner divertor tile. The particles found are composed of a mix of codeposited species up to 120 m in size with a thickness of 30-40 mu m, The main constituents are D from the fusion fuel, Be and W from the main plasma-facing components, and Ni and Cr from the Inconel grills of the antennas for auxiliary plasma heating. Elemental concentrations were estimated by iterative NRA-PIXE analysis. Two types of dust particles were found: (i) larger Be-rich particles with Be concentrations above 90 at% with a deuterium presence of up to 3.4 at% and containing Ni (1-3 at%), Cr (0.4-0.8 at%), W (0.2-0.9 at%), Fe (0.3-0.6 at%), and Cu and Ti in lower concentrations and (ii) small particles rich in Al and/or Si that were in some cases accompanied by other elements, such as Fe, Cu, or Ti or W and Mo.

  • 317. Feldstein, Y I
    et al.
    Gromova, L I
    Levitin, A E
    Blomberg, Lars
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marklund, Göran
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Lindqvist, Per-Arne
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Electromagnetic characteristics of the high-latitude ionosphere during the various phases of magnetic substorms1996Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 101, nr A9, s. 19921-19936Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Model calculations of the electrodynamics of the high-latitude ionosphere are compared to measurements made by the Viking satellite during July-August 1986. The model calculations are based on the IZMEM procedure, where the electric field and currents in the ionosphere are given as functions of the interplanetary magnetic field. The events chosen correspond to the growth, the expansion, and the recovery phases of substorms. During the growth and expansion phases the correlation between the model results and the satellite data is rather good. During recovery phase the correlation is not as good. The correlation between modeled and observed quantities suggest that during growth and expansion phase the magnetosphere is mainly directly driven by the solar wind, whereas during recovery phase it is mainly driven by internal processes, i.e., loading-unloading. Best fit is obtained when averaging the measured quantities over a few minutes, which means adjusting the spatial resolution of the measurements to the resolution of the model. Different time delays between the interplanetary magnetic field observations and those of Viking were examined. Best agreement was obtained, not surprisingly, for time delays corresponding to the estimated information transit time from the solar wind spacecraft to the ionosphere.

  • 318.
    Feldstein, Y. I.
    et al.
    IZMIRIAN, Troitsk, Russia.
    Gromova, L. I.
    IZMIRIAN, Troitsk, Russia.
    Levitin, A. E.
    IZMIRIAN, Troitsk, Russia.
    Blomberg, Lars
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marklund, Göran
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Lindqvist, Per-Arne
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    To directly driven and loading-unloading processes during substorm1996Ingår i: European Space Agency, (Special Publication) ESA SP, ISSN 03796566 (ISSN), nr 389, s. 69-74Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Model calculations of the electric fields in the high-latitude ionosphere are compared to measurements made by the Viking satellite during August 3, 1986 pass. The model calculations are based on the IZMEM procedure, where the electric field and currents in the ionosphere are given as functions of the interplanetary magnetic field (IMF). The event chosen correspond to the growth phase of substorm. The correlation between the model results and the satellite data is high, which assumes directly driven of the magnetosphere by the solar wind. Similar high correlation exists between the electric field in the solar wind (V*Bs) and AL magnetic activity indices, if time delays between the V*Bs observations in space and magnetic activity above the Earth's ground are taken into account. It is concluded, that the directly driven response of the magnetosphere to highly variable solar wind electric field is the main feature of geomagnetic activity at high latitudes.

  • 319.
    Feldstein, Y. I.
    et al.
    IZMIRIAN, Troitsk, Russia.
    Levitin, A. E.
    IZMIRIAN, Troitsk, Russia.
    Gromova, L. I.
    IZMIRIAN, Troitsk, Russia.
    DREMUHINA, LA
    Blomberg, Lars
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Lindqvist, Per-Arne
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marklund, Göran
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Electromagnetic weather at 100 km altitude on 3 August 19861994Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 21, s. 2095-2098Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electromagnetic weather at high altitudes above the Earth’s surface is determined by the transport of ionospheric plasma, which in turn is governed by the magnitude as well as the direction of the electric and magnetic fields. Different models [Levitin et al., 1984; Friis-Christensen et al., 1985; Mishin, 1990] have been proposed that allow an estimation of the electromagnetic parameters of the upper atmosphere, given a knowledge of the magnitude and orientation of the interplanetary magnetic field. Here we use one such model to estimate the global convection pattern and its temporal evolution during a pass of the Swedish satellite Viking over the northern polar cap. The model predictions are shown to agree well with the electric and magnetic fields measured along the satellite trajectory. The good agreement implies that the model can be used to reconstruct, with reasonable confidence, the large-scale distribution of electric and magnetic fields and their time-variation in the entire auroral ionosphere.

  • 320. Feldstein, Y. I.
    et al.
    Levitin, A. E.
    Gromova, L. I.
    Marklund, Göran
    KTH, Tidigare Institutioner (före 2005), Alfvénlaboratoriet.
    Blomberg, L. G.
    Lindqvist, Per-Arne
    KTH, Tidigare Institutioner (före 2005), Alfvénlaboratoriet.
    Electromagnetic weather over the high-latitude ionosphere during the aurora in the polar cap1995Ingår i: Cosmic research, ISSN 0010-9525, E-ISSN 1608-3075, Vol. 33, s. 326-335Artikel i tidskrift (Refereegranskat)
  • 321. Feldstein, Y. I.
    et al.
    Levitin, A. E.
    Gromova, L. I.
    Marklund, Göran
    KTH, Tidigare Institutioner (före 2005), Alfvénlaboratoriet.
    Blomberg, L. G.
    Lindqvist, Per-Arne
    KTH, Tidigare Institutioner (före 2005), Alfvénlaboratoriet.
    Elektromagnitnaya pogoda nad vysokoshirotnoj ionosferoj vo vremja poljarnogo sijanija v poljarnoj shapke1995Ingår i: Kosmicheskie Issledovaniya, Vol. 33, s. 360-370Artikel i tidskrift (Refereegranskat)
  • 322. Feldstein, Y. I.
    et al.
    Popov, V. A.
    Cumnock, Judy
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Prigancova, A.
    Blomberg, Lars G.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Kozyra, J. U.
    Tsurutani, B. T.
    Gromova, L. I.
    Levitin, A. E.
    Auroral electrojets and boundaries of plasma domains in the magnetosphere during magnetically disturbed intervals2006Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 24, nr 8, s. 2243-2276Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate variations in the location and intensity of the auroral electrojets during magnetic storms and substorms using a numerical method for estimating the equivalent ionospheric currents based on data from meridian chains of magnetic observatories. Special attention was paid to the complex structure of the electrojets and their interrelationship with diffuse and discrete particle precipitation and field-aligned currents in the dusk sector. During magnetospheric substorms the eastward electrojet (EE) location in the evening sector changes with local time from cusp latitudes (Phi similar to 77 degrees) during early afternoon to latitudes of diffuse auroral precipitation (Phi similar to 65 degrees) equatorward of the auroral oval before midnight. During the main phase of an intense magnetic storm the eastward currents in the noon-early evening sector adjoin to the cusp at Phi similar to 65 degrees and in the pre-midnight sector are located at subauroral latitude Phi similar to 57 degrees. The westward electrojet (WE) is located along the auroral oval from evening through night to the morning sector and adjoins to the polar electrojet (PE) located at cusp latitudes in the day-side sector. The integrated values of the eastward (westward) equivalent ionospheric current during the intense substorm are similar to 0.5 MA (similar to 1.5 MA), whereas they are 0.7 MA (3.0 MA) during the storm main phase maximum. The latitudes of auroral particle precipitation in the dusk sector are identical with those of both electrojets. The EE in the evening sector is accompanied by particle precipitation mainly from the Alfven layer but also from the near-Earth part of the central plasma sheet. In the lower-latitude part of the EE the field-aligned currents (FACs) flow into the ionosphere (Region 2 FAC), and at its higher-latitude part the FACs flow out of the ionosphere (Region 1 FAC). During intense disturbances, in addition to the Region 2 FAC and the Region 1 FAC, a Region 3 FAC with the downward current was identified. This FAC is accompanied by diffuse electron precipitation from the plasma sheet boundary layer. Actually, the triple system of FAC is observed in the evening sector and, as a consequence, the WE and the EE overlap. The WE in the evening sector comprises only the high-latitude periphery of the plasma precipitation region and corresponds to the Hall current between the Region 1 FAC and Region 3 FAC. During the September 1998 magnetic storm, two velocity bursts (similar to 2-4 km/s) in the magnetospheric convection were observed at the latitudes of particle precipitation from the central plasma sheet and at subauroral latitudes near the ionospheric trough. These kind of bursts are known as subauroral polarization streams (SAPS). In the evening sector the Alfven layer equatorial boundary for precipitating ions is located more equatorward than that for electrons. This may favour northward electric field generation between these boundaries and may cause high speed westward ions drift visualized as SAPS. Meanwhile, high speed ion drifts cover a wider range of latitudes than the distance between the equatorward boundaries of ions and electrons precipitation. To summarize the results obtained a new scheme of 3-D currents in the magnetosphere-ionosphere system and a clarified view of interrelated 3-D currents and magnetospheric plasma domains are proposed.

  • 323.
    Feldstein, Y. I.
    et al.
    IZMIRAN, Troitsk, Russia.
    Popov, V. A.
    IZMIRAN, Troitsk, Russia.
    Cumnock, Judy
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Prigancova, A.
    Blomberg, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Kozyra, J. U.
    Tsurutani, B. T.
    Gromova, L. I.
    IZMIRAN, Troitsk, Russia.
    Levitin, A. E.
    IZMIRAN, Troitsk, Russia.
    Auroral electrojets and 3D currents in the ionosphere-magnetosphere system2006Ingår i: “Physics of Auroral Phenomena”, Proc. XXIX Annual Seminar, Apatity, Kola Science Centre, Russian Academy of Science , 2006, s. 25-30Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    There are shortly described results of the analysis of variations in the location and intensity of the auroral electrojets during magnetic storms and substorms using a numerical method for estimating the equivalent ionospheric currents based on data from meridian chains of magnetic observatories. It is shown that the westward electrojet adjoins to the polar electrojet located at cusp latitudes in the dayside sector. The association of electrojets with the field-aligned currents (FACs), namely Region 1 FAC and Region 2 FAC is considered. During intense disturbances a Region 3 FAC (accompanied with diffuse electron precipitation from the plasma sheet boundary layer) with the downward current was identified. The analysis of observational data is summarized in terms of 2D time-latitude distribution of electrojets at ionospheric altitudes. The magnetic field sawtooth variations generated during the storm main and early recovery phases are also discussed. To follow 3D currents in the magnetosphereionosphere system a clarified view of interrelated 3D currents and magnetospheric plasma domains is presented.

  • 324.
    Feldstein, Y. I.
    et al.
    IZMIRAN, Troitsk, Russia.
    Prigancova, A.
    Vorobjev, V. G.
    Cumnock, Judy
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Starkov, G. V.
    Yagodkina, O. I.
    Blomberg, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    High-latitude electrojets and auroral luminosity and auroral particle precipitations2007Ingår i: “Physics of Auroral Phenomena”, Proc. XXX Annual Seminar, Apatity, Kola Science Centre, Russian Academy of Science , 2007, s. 55-59Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The mutual location of high-latitude electrojets, typical regions of the auroral luminosity and regions of auroral energy particle participations into the upper atmosphere under substorm conditions are considered. Three electrojets exist at high latitudes during substorm intervals: WE - westward electrojet, EE - eastward electrojet and PE – polar electrojet. Geomagnetic latitudes of the WE/EE and PE location vary depend on local time and magnetic activity level, respectively. It is shown that the WE is located within the limits of the auroral oval precipitation (AOP), the EE in the evening sector is located within the diffuse auroral zone (DAZ) and the PE near noon is located at the poleward AOP boundary shifting poleward with decreasing the magnetic activity level. The relationship of electrojets with different plasma domains in the magnetosphere is discussed.

  • 325. Feldstein, Y. I.
    et al.
    Woch, G. J.
    Sandahl, I.
    Blomberg, Lars G.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marklund, Göran T.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Meng, C. I.
    Structure of the auroral precipitation region in the dawn sector: relationship to convection reversal boundaries and field-aligned currents2001Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 19, nr 5, s. 495-519Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Simultaneous DMSP F7 and Viking satellite measurements of the dawnside high-latitude auroral energy electron and ion precipitation show that the region of the low and middle altitude auroral precipitation consists of three characteristic plasma regimes. The recommendation of the IAGA Working Group IIF/III4 at the IAGA Assembly in Boulder, July 1995 to decouple the nomenclature of ionospheric populations from magnetospheric population is used for their notation. The most equatorial regime is the Diffuse Auroral Zone (DAZ) of diffuse spatially unstructured precipitating electrons. It is generated by the plasma injection to the inner magnetosphere in the nightside and the subsequent drift plasma to the dawnside around the Earth. Precipitating par tides have a hard spectrum with typical energies of electrons and ions of more than 3 keV. In the DAZ, the ion pitch-angle distribution is anisotropic. with the peak near 90 degrees. The next part is the Auroral Oval (AO), a structured electron regime which closely resembles the poleward portion of the nightside auroral oval. The typical electron energy is several keV, and the ion energy is up to 10 keV. Ion distributions are predominantly isotropic. In some cases, this plasma regime may be absent in the prenoon sector. Poleward of the Auroral Oval, there is the Soft Small Scale Luminosity (SSSL) regime. It is caused by structured electron and ion precipitation with typical electron energy of about 0.3 keV and ion energy of about 1 keV. The connection of these low-altitude regimes with plasma domains of the distant magnetosphere is discussed. For mapping of the plasma regimes to the equatorial plane of the magnetosphere, the empirical model by Tsyganenko (1995) and the conceptual model by Alexeev et al. (1996) are used. The DAZ is mapped along the magnetic field lines to the Remnant Layer (RL), which is located in the outer radiation belt region: the zone of structured electrons and isotropic ion precipitation (AO) is mapped to the dawn periphery of the Central Plasma Sheet (CPS); the soft small scale structured precipitation (SSSL) is mapped to the outer magnetosphere close to the magnetopause, i.e. the Low Latitude Boundary Layer (LLBL). In the near-noon sector, earthward fluxes of soft electrons, which cause the Diffuse Red Aurora (DRA), are observed. The ion energies decrease with increasing latitude, The plasma spectra of the DRA regime are analogous to the spectra of the Plasma Mantle (PM). In the dawn sector, the large-scale field-aligned currents flow into the ionosphere at the SSSL latitudes (Region 1) and flow out at the AO or DAZ latitudes (Region 2). In the dawn and dusk sectors, the large-scale Region 1 and Region 2 FAC generation occurs in different plasma domains of the distant magnetosphere. The dawn and dusk FAC connection to the traditional Region 1 and Region 2 has only formal character, as FAC generating in various magnetospheric plasma domains integrate in the same region (Region 1 or Region 2). In the SSSL, there is anti-sunward convection in the DAZ and the AO, there is the sunward convection. At PM latitudes, the convection is controlled by the azimuthal IMF component (By) It is suggested to extend the notation of the plasma pattern boundaries, as proposed by Newell et al. (1996), for the nightside sector of the auroral oval to the dawn sector.

  • 326.
    Figueiredo, Sonia
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Karlsson, Tomas
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Marklund, Göran
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Investigation of subauroral ion drifts and related field-aligned currents and ionospheric Pedersen conductivity distribution2004Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 22, nr 3, s. 923-934Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Based on Astrid-2 satellite data, results are presented from a statistical study on subauroral ion drift (SAID) occurrence. SAID is a subauroral phenomenon characterized by a westward ionospheric ion drift with velocity greater than 1000 m/s, or equivalently, by a poleward-directed electric field with intensity greater than 30 mV/m. SAID events occur predominantly in the premidnight sector, with a maximum probability located within the 20:00 to 23:00 MLT sector, where the most rapid SAID events are also found. They are substorm related, and show first an increase in intensity and a decrease in latitudinal width during the expansion phase, followed by a weakening and widening of the SAID structures during the recovery phase. The potential drop across a SAID structure is seen to remain roughly constant during the recovery phase. The field-aligned current density and the height-integrated Pedersen conductivity distribution associated with the SAID events were calculated. The results reveal that the strongest SAID electric field peaks are associated with the lowest Pedersen conductivity minimum values. Clear modifications are seen in the ionospheric Pedersen conductivity distribution associated with the SAID structure as time evolves: the SAID peak is located on the poleward side of the corresponding region of reduced Pedersen conductivity; the shape of the regions of reduced conductivity is asymmetric, with a steeper poleward edge and a more rounded equatorward edge; the SAID structure becomes less intense and widens with evolution of the substorm recovery phase. From the analysis of the SAID occurrence relative to the mid-latitude trough position, SAID peaks are seen to occur relatively close to the corresponding mid-latitude trough minimum. Both these features show a similar response to magnetospheric disturbances, but on different time scales - with increasing magnetic activity, the SAID structure shows a faster movement towards lower latitudes than that of the mid-latitude trough. From the combined analysis of these results, we conclude that the SAID generation mechanism cannot be regarded either as a pure voltage generator or as a pure current generator, applied to the ionosphere. While the anti-correlation between the width and the peak intensity of the SAID structures with substorm evolution indicates a magnetospheric source acting as a constant voltage generator, the ionospheric modifications and, in particular the reduction in the conductivity for intense SAID structures, are indicative of a constant current system closing through the ionosphere. The ionospheric feedback mechanisms are seen to be of major importance for sustaining and regulating the SAID structures.

  • 327.
    Figueiredo, Sonia
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Marklund, Göran
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Karlsson, Tomas
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Johansson, Tommy
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Ebihara, Y
    Ejiri, M
    Ivchenko, Nickolay
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Lindqvist, Per-Arne
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Nilsson, H
    Fazakerley, A
    Temporal and spatial evolution of discrete auroral arcs as seen by Cluster2005Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 23, nr 7, s. 2531-2557Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two event studies are presented in this paper where intense convergent electric fields, with mapped intensities up to 1350 mV/m, are measured in the auroral upward current region by the Cluster spacecraft, at altitudes between 3 and 5 Earth radii. Both events are from May 2003, Southern Hemisphere, with equatorward crossings by the Cluster spacecraft of the pre-midnight auroral oval. Event 1 occurs during the end of the recovery phase of a strong substorm. A system of auroral arcs associated with convergent electric field structures, with a maximum perpendicular potential drop of about similar to 10 kV, and upflowing field-aligned currents with densities of 3 mu A/m(2) (mapped to the ionosphere), was detected at the boundary between the Plasma Sheet Boundary Layer (PSBL) and the Plasma Sheet (PS). The auroral arc structures evolve in shape and in magnitude on a timescale of tens of minutes, merging, broadening and intensifying, until finally fading away after about 50 min. Throughout this time, both the PS region and the auroral arc structure in its poleward part remain relatively fixed in space, reflecting the rather quiet auroral conditions during the end of the substorm. The auroral upward acceleration region is shown for this event to extend beyond 3.9 Earth radii altitude. Event 2 occurs during a more active period associated with the expansion phase of a moderate substorm. Images from the Defense Meteorological Satellite Program (DMSP) F13 spacecraft show that the Cluster spacecraft crossed the horn region of a surge-type aurora. Conjugated with the Cluster spacecraft crossing above the surge horn, the South Pole All Sky Imager recorded the motion and the temporal evolution of an east-west aligned auroral arc, 30 to 50 km wide. Intense electric field variations are measured by the Cluster spacecraft when crossing above the auroral arc structure, collocated with the density gradient at the PS poleward boundary, and coupled to intense upflowing field-aligned currents with mapped densities of up to 20 mu A/m(2). The surge horn consists of multiple arc structures which later merge into one structure and intensify at the PS poleward boundary. The surge horn and the associated PS region moved poleward with a velocity at the ionospheric level of 0.5 km/s, following the large-scale poleward expansion of the auroral oval associated with the substorm expansion phase.

  • 328.
    Figueiredo, Sónia
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Investigation of subauroral electric fields in the Earth's ionosphere based on Astrid-2 data2001Självständigt arbete på avancerad nivå (yrkesexamen), 40 poäng / 60 hpStudentuppsats (Examensarbete)
  • 329. Finnegan, S. M.
    et al.
    Koepke, Mark
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Knudsen, D. J.
    The dispersive Alfven wave in the time-stationary limit with a focus on collisional and warm-plasma effects2008Ingår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 15, nr 5, s. 052108-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A nonlinear, collisional, two-fluid model of uniform plasma convection across a field-aligned current (FAC) sheet, describing the stationary Alfven (StA) wave, is presented. In a previous work, Knudsen showed that, for cold, collisionless plasma [D. J. Knudsen, J. Geophys. Res. 101, 10761 (1996)], the stationary inertial Alfven (StIA) wave can accelerate electrons parallel to a background magnetic field and cause large, time-independent plasma-density variations having spatial periodicity in the direction of the convective flow over a broad range of spatial scales and energies. Knudsen suggested that these fundamental properties of the StIA wave may play a role in the formation of discrete auroral arcs. Here, Knudsen's model has been generalized for warm, collisional plasma. From this generalization, it is shown that nonzero ion-neutral and electron-ion collisional resistivity significantly alters the perpendicular ac and dc structure of magnetic-field-aligned electron drift, and can either dissipate or enhance the field-aligned electron energy depending on the initial value of field-aligned electron drift velocity. It is also shown that nonzero values of plasma pressure increase the dominant Fourier component of perpendicular wavenumber.

  • 330.
    Forsberg, Peter
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    A study of strong electric fields observed by Freja at low altitudes1996Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 331.
    Forslund, Åke
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Designing a miniaturized fluxgate magnetometer2006Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    SMILE (Small Magnetometer In Low-mass Experiment) is a digital fluxgate magnetometer designed with miniaturization as a goal. The instrument is intended asa payload for the Microlink (previously Nanospace) satellite. SMILE operates onsimilar principles as the magnetometer onboard Astrid-2 satellite. The magnetic fieldcomponents are extracted from the pick-up signal by means of digital correlation witha set of reference coefficients. An important difference from the Astrid-2magnetometer is that the digital signal processing previously done in threeprocessors (one for each axis) has been replaced with a single FPGA to achieve asmaller circuit board area. A new miniaturized fluxgate sensor with volumecompensation produced by the Lviv Center of Institute of Space Research is used inthe design. A prototype board was designed and built at the Royal Institute of Technology.Gateware suitable for calibration has been completed. Gateware for the operationalinstrument is still in its final stage of development.

  • 332. Fortuna, E.
    et al.
    Rubel, Marek J.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Philipps, V.
    Kurzydlowski, K. J.
    Mertens, Ph.
    Miskiewicz, M.
    Pisarek, M.
    Van Oost, G.
    Zielinski, W.
    Properties of co-deposited layers on graphite high heat flux components at the TEXTOR tokamak2007Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 367, nr B, s. 1507-1511Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The objective of this work was to examine the structure, composition and properties of co-deposited films from the TEXTOR tokamak. Hydrogenated films formed on the toroidal belt pump limiter (ALT-II), and on the ICRF antenna grill were studied using a set of material analysis techniques. Plasma edge diagnostics were used to assess the parameters influencing the film formation during discharges auxiliary heated by ICRF. The essential results are summarized as follows: (i) the distribution of plasma impurities co-deposited in the films is non-uniform and (ii) the surface topography, crystallographic structure, fuel retention and composition (i.e., content of re-deposited plasma impurities) of the films show significant diversity depending on the location where they were formed. These differences are associated with the local geometry, the tokamak operation scenarios and the resulting plasma edge properties.

  • 333. Fortuna, E.
    et al.
    Rubel, Marek J.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Psoda, M.
    Andrzejczuk, M.
    Kurzydlowski, K. J.
    Miskiewicz, M.
    Philipps, V.
    Pospieszczyk, A.
    Sergienko, G.
    Spychalski, M.
    Zielinski, W.
    Plasma-induced damage of tungsten coatings on graphite limiters2007Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T128, s. 162-165Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vaccum plasma sprayed tungsten coatings with an evaporated sandwich Re - W interlayer on graphite limiter blocks were studied after the experimental campaign in the TEXTOR tokamak. The coating morphology was modified by high-heat loads and co-deposition of species from the plasma. Co-deposits contained fuel species, carbon, boron and silicon. X-ray diffractometer phase analysis indicated the coexistence of metallic tungsten and its carbides (WC and W2C) and boride (W2B). In the Re - W layer the presence of carbon was detected in a several micrometres thick zone. In the overheated part of the limiter, the Re - W layer was transformed into a sigma phase.

  • 334. Fortuna-Zalesna, E.
    et al.
    Grzonka, J.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Garcia Carrasco, Alvaro
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Widdowson, A.
    Baron-Wiechec, A.
    Ciupinski, L.
    Studies of dust from JET with the ITER-Like Wall: Composition and internal structure2017Ingår i: NUCLEAR MATERIALS AND ENERGY, ISSN 2352-1791, Vol. 12, s. 582-587Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Results are presented for the dust survey performed at JET after the second experimental campaign with the ITER-Like Wall: 2013-2014. Samples were collected on adhesive stickers from several different positions in the divertor both on the tiles and on the divertor carrier. Brittle dust-forming deposits on test mirrors from the inner divertor wall were also studied. Comprehensive characterization accomplished by a wide range of high-resolution microscopy techniques, including focused ion beam, has led to the identification of several classes of particles: (i) beryllium flakes originating either from the Be coatings from the inner wall cladding or Be-rich mixed co-deposits resulting from material migration; (ii) beryllium droplets and splashes; (iii) tungsten and nickel-rich (from Inconel) droplets; (iv) mixed material layers with a various content of small (8-200 nm) W-Mo and Ni-based debris. A significant content of nitrogen from plasma edge cooling has been identified in all types of co-deposits. A comparison between particles collected after the first and second experimental campaign is also presented and discussed.

  • 335. Fortuna-Zalesna, E.
    et al.
    Weckmann, Armin
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Grozonka, J.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Esser, H. G.
    Freisinger, M.
    Kreter, A.
    Kischner, A.
    Sergienko, G.
    Ström, Petter
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Dust Survey Following the Final Shutdown of TEXTOR: Metal Particles and Fuel Retention2016Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T167, artikel-id 014059Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The work presents results of a broad TEXTOR dust survey in terms of its composition, structure, distribution and fuel content. The dust particles were collected after final shutdown of TEXTOR in December 2013. Fuel retention, as determined by thermal desorption, varied significantly, even by two orders of magnitude, dependent on the dust location in the machine. Dust structure was examined by means of scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, focused ion beam and scanning transmission electron microscopy. Several categories of dust have been identified. Carbon-based stratified and granular deposits were dominating, but the emphasis in studies was on metal dust. They were found in the form of small particles, small spheres, flakes and splashes which formed “comet”-like structures clearly indicating directional effects in the impact on surfaces of plasma-facing components. Nickel-rich alloys from the Inconel liner and iron-based ones from various diagnostic holders were the main components of metal-containing dust, but also molybdenum and tungsten debris were detected. Their origin is discussed.

  • 336. Franz, P
    et al.
    Marrelli, L
    Piovesan, P
    Predebon, I
    Bonomo, F
    Frassinetti, Lorenzo
    Consorzio RFX.
    Martin, P
    Spizzo, G
    Chapman, BE
    Craig, D.
    Sarff, J. S.
    Tomographic imaging of resistive mode dynamics in the Madison Symmetric Torus reversed-field pinch2006Ingår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 13, nr 1, s. 012510-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A detailed study of the dynamics and magnetic topological effects of resistive-tearing modes is presented for different operational regimes in the Madison Symmetric Torus reversed-field pinch [R. N. Dexter , Fusion Technol. 19, 131 (1991)]. Soft-x-ray tomography and magnetic measurements, along with numerical reconstruction of magnetic-field lines with the ORBIT code [R. B. White and M. S. Chance, Phys. Fluids 27, 2455 (1984)], have been employed. Magnetic-mode dynamics has been investigated in standard plasmas during the transition to the quasi-single helicity state, in which a single mode dominates the mode spectrum. Single helical soft-x-ray structures are studied with tomography in these cases. These structures are associated with magnetic islands, indicating that helical flux surfaces appear in the plasma. Mode dynamics has also been examined during auxiliary inductive current drive, the goal of which is to reduce the tearing-mode amplitudes. In this case the phenomenology of the soft-x-ray structures appearing in the plasma is more complex. In fact, when a quasi-single helicity spectrum occurs, a single island bigger than in the standard case is usually found. On the other hand, when all modes decrease, two helical soft-x-ray structures are observed, with the same helicity as the two innermost resonant modes. This constitutes the first direct evidence of magnetic-chaos reduction during auxiliary inductive current drive, which is responsible for the achievement of the best confinement in the reversed-field pinch configuration up to now.

  • 337.
    Frassinetti, Lorenzo
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Inter-ELM evolution of the pedestal structure in JET-ILW2016Ingår i: 24th European Fusion Physics Workshop, 28-30 November 2016, 2016Konferensbidrag (Övrigt vetenskapligt)
  • 338.
    Frassinetti, Lorenzo
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Magnetic perturbation and dynamo generation effects on 3-d flows in RFPs2010Ingår i: 18th European Fusion Physics Workshop, December 2010, Mayrhofen, Austria, 2010Konferensbidrag (Övrigt vetenskapligt)
  • 339.
    Frassinetti, Lorenzo
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Wall diffusion time in EXTRAP T2R and possible applications to tokamaks2012Konferensbidrag (Övrigt vetenskapligt)
  • 340.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Beurskens, M
    ELM losses in high triangularity plasmas in JET with the metal and carbon wall2012Ingår i: EFDA-JET Science Meeting on ELM Studies, June 25, 2012, 2012Konferensbidrag (Övrigt vetenskapligt)
  • 341.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Beurskens, M
    Study on global and pedestal confinement in metal and carbon wall2012Ingår i: EFDA-JET Science Meeting on Pedestal Studies, June 11, 2012, 2012Konferensbidrag (Övrigt vetenskapligt)
  • 342.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Beurskens, M
    Alper, B
    Bourdelle, C
    Brezinsek, S
    Bucalossi, J
    Buratti, P
    Crisanti, C
    Challis, C
    Flanagan, J
    Giroud, C
    Groth, M
    Hobirk, J
    Joffrin, E
    Leyland, M
    Lomas, P
    Kampeenars, M
    Maslov, M
    Matthews, G
    Mayoral, M
    McCormick, K
    Neu, R
    Nunes, I
    Rimini, F
    Saarelma, S
    Core versus edge confinement in JET with the ILW compared to the CFC first-wall2012Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics, 2012, s. 1334-1337Konferensbidrag (Refereegranskat)
  • 343.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Beurskens, M. N. A.
    Saarelma, S.
    Boom, J. E.
    Delabie, E.
    Flanagan, J.
    Kempenaars, M.
    Giroud, C.
    Lomas, P.
    Meneses, L.
    Maggi, C. S.
    Menmuir, S.
    Nunes, I.
    Rimini, F.
    Stefanikova, E.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Urano, H.
    Verdoolaege, G.
    Global and pedestal confinement and pedestal structure in dimensionless collisionality scans of low-triangularity H-mode plasmas in JET-ILW2017Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, nr 1, artikel-id 061012Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A dimensionless collisionality scan in low-triangularity plasmas in the Joint European Torus with the ITER-like wall (JET-ILW) has been performed. The increase of the normalized energy confinement (defined as the ratio between thermal energy confinement and Bohm confinement time) with decreasing collisionality is observed. Moreover, at low collisionality, a confinement factor H-98, comparable to JET-C, is achieved. At high collisionality, the low normalized confinement is related to a degraded pedestal stability and a reduction in the density-profile peaking. The increase of normalized energy confinement is due to both an increase in the pedestal and in the core regions. The improvement in the pedestal is related to the increase of the stability. The improvement in the core is driven by (i) the core temperature increase via the temperature-profile stiffness and by (ii) the density-peaking increase driven by the low collisionality. Pedestal stability analysis performed with the ELITE (edge-localized instabilities in tokamak equilibria) code has a reasonable qualitative agreement with the experimental results. An improvement of the pedestal stability with decreasing collisionality is observed. The improvement is ascribed to the reduction of the pedestal width, the increase of the bootstrap current and the reduction of the relative shift between the positions of the pedestal density and pedestal temperature. The EPED1 model predictions for the pedestal pressure height are qualitatively well correlated with the experimental results. Quantitatively, EPED1 overestimates the experimental pressure by 15-35%. In terms of the pedestal width, a correct agreement (within 10-15%) between the EPED1 and the experimental width is found at low collisionality. The experimental pedestal width increases with collisionality. Nonetheless, an extrapolation to low-collisionality values suggests that the width predictions from the KBM constraint are reasonable for ITER.

  • 344.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Beurskens, M. N. A.
    Scannell, R.
    Osborne, T. H.
    Flanagan, J.
    Kempenaars, M.
    Maslov, M.
    Pasqualotto, R.
    Walsh, M.
    Spatial resolution of the JET Thomson scattering system2012Ingår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 83, nr 1, s. 013506-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The instrument function of the high resolution Thomson scattering (HRTS) diagnostic in the Joint European Torus (JET) has been calculated for use in improved pedestal profile analysis. The full width at half maximum (FWHM) of the spatial instrument response is (22 +/- 1) mm for the original HRTS system configuration and depends on the particular magnetic topology of the JET plasmas. An improvement to the optical design of the laser input system is presented. The spatial smearing across magnetic flux surfaces is reduced in this design. The new input system has been implemented (from JPN 78742, July 2009) and the HRTS instrument function corresponding to the new configuration has been improved to approximately FWHM = (9.8 +/- 0.8) mm. The reconstructed instrument kernels are used in combination with an ad hoc forward deconvolution procedure for pedestal analysis. This procedure produces good results for both the old and new setups, but the reliability of the deconvolved profiles is greatly reduced when the pedestal width is of the same order as, or less than the FWHM of the instrument kernel.

  • 345.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Beurskens, M
    Saarelma, S
    Global and pedestal confinement and pedestal structure in dimensionless collisionality scans of low triangularity H-mode plasmas in JET-ILW2015Ingår i: ITPA-PEP meeting, 22-23 October 2015, 2015Konferensbidrag (Övrigt vetenskapligt)
  • 346.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Beurskens, M.N.A.
    McDonald, D.C.
    Hobirk, J.
    Zarzoso, D.
    Buratti, P.
    Crisanti, F.
    Challis, C.
    Giovannozzi, E.
    Joffrin, E.
    Lomas, P.
    Lonnroth, J.
    Maggi, C.
    Nunes, I.
    Saarelma, S.
    Saibene, G.
    et al.,
    Pedestal confinement in hybrid versus baseline plasmas in JET2010Ingår i: 37th European Physical Society Conference on Plasma Physics. Contributed Papers, 2010, s. P1.1031-Konferensbidrag (Refereegranskat)
  • 347.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Brunsell, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Cecconello, Marco
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Drake, James R.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Khan, Muhammad Waqas Mehmood
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Menmuir, Sheena
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Olofsson, Erik
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Active feedback control of QSH in EXTRAP-T2R2008Konferensbidrag (Refereegranskat)
  • 348.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Brunsell, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Drake, James Robert
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Menmuir, Sheena
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Cecconello, Marco
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Spontaneous QSH in the EXTRAP T2R reversed-field pinch2007Ingår i: 34th EPS Conference on Plasma Physics 2007, EPS 2007 - Europhysics Conference Abstracts, 2007, s. 579-582Konferensbidrag (Refereegranskat)
  • 349.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Brunsell, Per R.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Drake, James R.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Experiments and modelling of active quasi-single helicity regime generation in a reversed field pinch2009Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 49, nr 7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The interaction of a static resonant magnetic perturbation (RMP) with a tearing mode (TM) is becoming a relevant topic in fusion plasma physics. RMPs can be generated by active coils and then used to affect the properties of TMs and of the corresponding magnetic islands. This paper shows how the feedback system of the EXTRAP T2R reversed field pinch (RFP) can produce a RMP that affects a rotating TM and stimulate the transition to the so-called quasi-single helicity (QSH) regime, a RFP plasma state characterized by a magnetic island surrounded by low magnetic chaos. The application of the RMP can increase the QSH probability up to 10% and enlarge the size of the corresponding island. Part of the experimental results are supported by a theoretical study that models the effect of the active coils on the magnetic island.

  • 350.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Brunsell, Per R.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Drake, James R.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Heat transport in the quasi-single-helicity islands of EXTRAP T2R2009Ingår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 16, nr 3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The heat transport inside the magnetic island generated in a quasi-single-helicity regime of a reversed-field pinch device is studied by using a numerical code that simulates the electron temperature and the soft x-ray emissivity. The heat diffusivity chi(e) inside the island is determined by matching the simulated signals with the experimental ones. Inside the island, chi(e) turns out to be from one to two orders of magnitude lower than the diffusivity in the surrounding plasma, where the magnetic field is stochastic. Furthermore, the heat transport properties inside the island are studied in correlation with the plasma current and with the amplitude of the magnetic fluctuations.

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