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  • 1.
    Graham, Daniel B.
    et al.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Khotyaintsev, Yuri V.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Vaivads, Andris
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Andre, Mats
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Electrostatic solitary waves and electrostatic waves at the magnetopause2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 4, p. 3069-3092Article in journal (Refereed)
    Abstract [en]

    Electrostatic solitary waves (ESWs) are characterized by localized bipolar electric fields parallel to the magnetic field and are frequently observed in space plasmas. In this paper a study of ESWs and field-aligned electrostatic waves, which do not exhibit localized bipolar fields, near the magnetopause is presented using the Cluster spacecraft. The speeds, length scales, field strengths, and potentials are calculated and compared with the local plasma conditions. A large range of speeds is observed, suggesting different generation mechanisms. In contrast, a smaller range of length scales normalized to the Debye length lambda(D) is found. For ESWs the average length between the positive and negative peak fields is 9 lambda(D), comparable to the average half wavelength of electrostatic waves. Statistically, the lengths and speeds of ESWs and electrostatic waves are shown to be similar. The length scales and potentials of the ESWs are consistent with predictions for stable electron holes. The maximum ESW potentials are shown to be constrained by the length scale and the magnetic field strength at the magnetopause and in the magnetosheath. The observed waves are consistent with those generated by the warm bistreaming instability, beam-plasma instability, and electron-ion instabilities, which account for the observed speeds and length scales. The large range of wave speeds suggests that the waves can couple different electron populations and electrons with ions, heating the plasma and contributing to anomalous resistivity.

  • 2.
    Graham, Daniel B.
    et al.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Khotyaintsev, Yuri V.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Vaivads, Andris
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    André, Mats
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Electrostatic solitary waves with distinct speeds associated with asymmetric reconnection2015In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, no 2, p. 215-224Article in journal (Refereed)
    Abstract [en]

    Electrostatic solitary waves (ESWs) are observed at the magnetopause with distinct time scales. These ESWs are associated with asymmetric reconnection of the cold dense magnetosheath plasma with the hot tenuous magnetospheric plasma. The distinct time scales are shown to be due to ESWs moving at distinct speeds and having distinct length scales. The length scales are of order 5-50 Debye lengths, and the speeds range from approximate to 50 km s(-1) to approximate to 1000 km s(-1). The ESWs are observed near the reconnection separatrices. The observation of ESWs with distinct speeds suggests that multiple instabilities are occurring. The implications for reconnection at the magnetopause are discussed.

  • 3.
    Graham, Daniel B.
    et al.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Khotyaintsev, Yuri V.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Vaivads, Andris
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    André, Mats
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Fazakerley, A. N.
    Electron Dynamics in the Diffusion Region of an Asymmetric Magnetic Reconnection2014In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 112, no 21, p. 215004-Article in journal (Refereed)
    Abstract [en]

    During a magnetopause crossing near the subsolar point Cluster observes the ion diffusion region of antiparallel magnetic reconnection. The reconnecting plasmas are asymmetric, differing in magnetic field strength, density, and temperature. Spatial changes in the electron distributions in the diffusion region are resolved and investigated in detail. Heating of magnetosheath electrons parallel to the magnetic field is observed. This heating is shown to be consistent with trapping of magnetosheath electrons by parallel electric fields.

  • 4.
    Graham, Daniel. B.
    et al.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Vaivads, Andris
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Khotyaintsev, Yuri. V.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Andre, Mats
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Whistler emission in the separatrix regions of asymmetric magnetic reconnection2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 3, p. 1934-1954Article in journal (Refereed)
    Abstract [en]

    At Earth's dayside magnetopause asymmetric magnetic reconnection occurs between the cold dense magnetosheath plasma and the hot tenuous magnetospheric plasma, which differs significantly from symmetric reconnection. During magnetic reconnection the separatrix regions are potentially unstable to a variety of instabilities. In this paper observations of the separatrix regions of asymmetric reconnection are reported as Cluster crossed the magnetopause near the subsolar point. The small relative motion between the spacecraft and plasma allows spatial changes of electron distributions within the separatrix regions to be resolved over multiple spacecraft spins. The electron distributions are shown to be unstable to the electromagnetic whistler mode and the electrostatic beam mode. Large-amplitude whistler waves are observed in the magnetospheric and magnetosheath separatrix regions, and outflow region. In the magnetospheric separatrix regions the observed whistler waves propagate toward the X line, which are shown to be driven by the loss in magnetospheric electrons propagating away from the X line and are enhanced by the presence of magnetosheath electrons. The beam mode waves are predicted to be produced by beams of magnetosheath electrons propagating away from the X line and potentially account for some of the electrostatic fluctuations observed in the magnetospheric separatrix regions.

  • 5.
    Huang, S. Y.
    et al.
    Wuhan Univ, Sch Elect Informat, Wuhan, Peoples R China.;UPMC, Lab Phys Plasmas, CNRS, Ecole Polytech, Palaiseau, France..
    Fu, H. S.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China..
    Yuan, Z. G.
    Wuhan Univ, Sch Elect Informat, Wuhan, Peoples R China..
    Vaivads, Andris
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Khotyaintsev, Yuri V.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Retino, A.
    UPMC, Lab Phys Plasmas, CNRS, Ecole Polytech, Palaiseau, France..
    Zhou, M.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang, Peoples R China..
    Graham, Daniel B.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Fujimoto, K.
    Natl Astron Observ Japan, Div Theoret Astron, Mitaka, Tokyo, Japan..
    Sahraoui, F.
    UPMC, Lab Phys Plasmas, CNRS, Ecole Polytech, Palaiseau, France..
    Deng, X. H.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang, Peoples R China..
    Ni, B.
    Wuhan Univ, Sch Elect Informat, Wuhan, Peoples R China..
    Pang, Y.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang, Peoples R China..
    Fu, S.
    Wuhan Univ, Sch Elect Informat, Wuhan, Peoples R China..
    Wang, D. D.
    Wuhan Univ, Sch Elect Informat, Wuhan, Peoples R China..
    Zhou, X.
    Liaoning Univ, Sch Phys, Shenyang, Peoples R China..
    Two types of whistler waves in the hall reconnection region2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 7, p. 6639-6646Article in journal (Refereed)
    Abstract [en]

    Whistler waves are believed to play an important role during magnetic reconnection. Here we report the near-simultaneous occurrence of two types of the whistler-mode waves in the magnetotail Hall reconnection region. The first type is observed in the magnetic pileup region of downstream and propagates away to downstream along the field lines and is possibly generated by the electron temperature anisotropy at the magnetic equator. The second type, propagating toward the X line, is found around the separatrix region and probably is generated by the electron beam-driven whistler instability or erenkov emission from electron phase-space holes. These observations of two different types of whistler waves are consistent with recent kinetic simulations and suggest that the observed whistler waves are a consequence of magnetic reconnection.

  • 6.
    Huang, S. Y.
    et al.
    Wuhan Univ, Sch Elect Informat, Wuhan, Hubei, Peoples R China.
    Yuan, Z. G.
    Wuhan Univ, Sch Elect Informat, Wuhan, Hubei, Peoples R China.
    Fu, H. S.
    Beihang Univ, Sch Astronaut, Space Sci Inst, Beijing, Peoples R China.
    Vaivads, Andris
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Sahraoui, F.
    UPMC, EcolePolytech, CNRS, Lab Phys Plasmas, Palaiseau, France.
    Khotyaintsev, Yuri V.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Retino, A.
    UPMC, EcolePolytech, CNRS, Lab Phys Plasmas, Palaiseau, France.
    Zhou, M.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang, Jiangxi, Peoples R China.
    Graham, Daniel B.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Fujimoto, K.
    Natl Astron Observ Japan, Div Theoret Astron, Mitaka, Tokyo, Japan.
    Deng, X. H.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang, Jiangxi, Peoples R China.
    Ni, B. B.
    Wuhan Univ, Sch Elect Informat, Wuhan, Hubei, Peoples R China.
    Pang, Y.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang, Jiangxi, Peoples R China.
    Fu, S.
    Wuhan Univ, Sch Elect Informat, Wuhan, Hubei, Peoples R China.
    Wang, D. D.
    Wuhan Univ, Sch Elect Informat, Wuhan, Hubei, Peoples R China.
    Observations of Whistler Waves in the Magnetic Reconnection Diffusion Region2018In: 2ND URSI ATLANTIC RADIO SCIENCE MEETING (AT-RASC), IEEE , 2018Conference paper (Refereed)
    Abstract [en]

    Whistler waves are believed to play an important role during magnetic reconnection. In this paper, we report the simultaneous occurrence of two types of the whistler waves in the magnetotail reconnection diffusion region. The first type is observed in the pileup region of downstream and propagates away along the field lines to downstream, and is possibly generated by the electron temperature anisotropy at the magnetic equator. The second type is found around the separatrix region and propagates towards the X-line, and is possibly aenerated by the electron beam-driven whistler instability or Cerenkov emission from electron phase-space holes. Our observations of two different types of whistler waves are well consistent with recent kinetic simulations, and suggest that the observed whistler waves are the consequences of magnetic reconnection.Moreover, we statistically investigate the whistler waves in the magnetotail reconnection region, and construct the global distribution and occurrence rate of the whistler waves based on the two-dimensional reconnection model. It is found that the occurrence rate of the whistler waves is large in the separatrix region (113,1B0j>0.4) and pileup region ([B,./Bol<0.2, 161>45'), but very small in the X-line region. The statistical results are well consistent with the case study.

  • 7.
    Li, Wenya
    et al.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Andre, Mats
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Khotyaintsev, Yuri V.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Vaivads, Andris
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Graham, Daniel B.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Toledo-Redondo, S.
    European Space Agcy, Sci Directorate, ESAC, Madrid, Spain..
    Norgren, Cecilia
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Henri, P.
    CNRS, LPC2E, Orleans, France..
    Wang, C.
    Natl Space Sci Ctr, Beijing, Peoples R China..
    Tang, B. B.
    Natl Space Sci Ctr, Beijing, Peoples R China..
    Lavraud, B.
    Univ Toulouse UPS, Inst Rech Astrophys & Planetol, Toulouse, France.;CNRS, UMR 5277, Toulouse, France..
    Vernisse, Y.
    Univ Toulouse UPS, Inst Rech Astrophys & Planetol, Toulouse, France..
    Turner, D. L.
    Aerosp Corp, Dept Space Sci, El Segundo, CA 90245 USA..
    Burch, J.
    Southwest Res Inst, San Antonio, TX USA..
    Torbert, R.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Magnes, W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90024 USA..
    Blake, J. B.
    Aerosp Corp, Dept Space Sci, El Segundo, CA 90245 USA..
    Mauk, B.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Giles, B.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Pollock, C.
    Denali Sci, Healy, AL USA..
    Fennell, J.
    Aerosp Corp, Dept Space Sci, El Segundo, CA 90245 USA..
    Jaynes, A.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Avanov, L. A.
    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.;Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Paterson, W. R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Saito, Y.
    Japan Aerosp Explorat Agcy, Tokyo, Japan..
    Strangeway, R. J.
    Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90024 USA..
    Kinetic evidence of magnetic reconnection due to Kelvin-Helmholtz waves2016In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 11, p. 5635-5643Article in journal (Refereed)
    Abstract [en]

    The Kelvin-Helmholtz (KH) instability at the Earth's magnetopause is predominantly excited during northward interplanetary magnetic field (IMF). Magnetic reconnection due to KH waves has been suggested as one of the mechanisms to transfer solar wind plasma into the magnetosphere. We investigate KH waves observed at the magnetopause by the Magnetospheric Multiscale (MMS) mission; in particular, we study the trailing edges of KH waves with Alfvenic ion jets. We observe gradual mixing of magnetospheric and magnetosheath ions at the boundary layer. The magnetospheric electrons with energy up to 80keV are observed on the magnetosheath side of the jets, which indicates that they escape into the magnetosheath through reconnected magnetic field lines. At the same time, the low-energy (below 100eV) magnetosheath electrons enter the magnetosphere and are heated in the field-aligned direction at the high-density edge of the jets. Our observations provide unambiguous kinetic evidence for ongoing reconnection due to KH waves.

  • 8.
    Norgren, Cecilia
    et al.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    André, Mats
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Graham, Daniel. B.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Khotyaintsev, Yuri. V.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Vaivads, Andris
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Slow electron holes in multicomponent plasmas2015In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, no 18, p. 7264-7272Article in journal (Refereed)
    Abstract [en]

    Electrostatic solitary waves (ESWs), often interpreted as electron phase space holes, are commonly observed in plasmas and are manifestations of strongly nonlinear processes. Often slow ESWs are observed, suggesting generation by the Buneman instability. The instability criteria, however, are generally not satisfied. We show how slow electron holes can be generated by a modified Buneman instability in a plasma that includes a slow electron beam on top of a warm thermal electron background. This lowers the required current for marginal instability and allows for generation of slow electron holes for a wide range of beam parameters that covers expected plasma distributions in space, for example, in magnetic reconnection regions. At higher beam speeds, the electron-electron beam instability becomes dominant instead, producing faster electron holes. The range of phase speeds for this model is consistent with a statistical set of observations at the magnetopause made by Cluster.

  • 9. Toledo-Redondo, Sergio
    et al.
    Andre, Mats
    Khotyaintsev, Yuri V.
    Lavraud, Benoit
    Vaivads, Andris
    Graham, Daniel B.
    Li, Wenya
    Perrone, Denise
    Fuselier, Stephen
    Gershman, Daniel J.
    Aunai, Nicolas
    Dargent, Jeremy
    Giles, Barbara
    Le Contel, Olivier
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Ergun, Robert E.
    Russell, Christopher T.
    Burch, James L.
    Energy budget and mechanisms of cold ion heating in asymmetric magnetic reconnection2017In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 9, p. 9396-9413Article in journal (Refereed)
    Abstract [en]

    Cold ions (few tens of eV) of ionospheric origin are commonly observed on the magnetospheric side of the Earth's dayside magnetopause. As a result, they can participate in magnetic reconnection, changing locally the reconnection rate and being accelerated and heated. We present four events where cold ion heating was observed by the Magnetospheric Multiscale mission, associated with the magnetospheric Hall E field region of magnetic reconnection. For two of the events the cold ion density was small compared to the magnetosheath density, and the cold ions were heated roughly to the same temperature as magnetosheath ions inside the exhaust. On the other hand, for the other two events the cold ion density was comparable to the magnetosheath density and the cold ion heating observed was significantly smaller. Magnetic reconnection converts magnetic energy into particle energy, and ion heating is known to dominate the energy partition. We find that at least 10-25% of the energy spent by reconnection into ion heating went into magnetospheric cold ion heating. The total energy budget for cold ions may be even higher when properly accounting for the heavier species, namely helium and oxygen. Large E field fluctuations are observed in this cold ion heating region, i.e., gradients and waves, that are likely the source of particle energization. Plain Language Summary The magnetic field of Earth creates a natural shield that isolates and protects us from the particles and fields coming from our star, the Sun. This natural shield is called the magnetosphere and is filled by plasma. The particles coming from the Sun form another plasma called the solar wind and are usually deviated around the magnetosphere. However, under certain circumstances these two plasmas can reconnect (magnetic reconnection), and part of the energy and mass of the two plasmas is interchanged. Magnetic reconnection is the driver of storms and substorms inside the magnetosphere. In this work, we investigate what occurs to particles of very low energy (cold ions) of ionospheric origin when they reach the reconnecting boundary of the magnetosphere. It is found that they are energized and take an important part of the energy spent in reconnecting the plasmas. The plasma boundary develops spatial structures and emits waves that are able to heat the cold ions. Once heated, these cold ions irreversibly will escape the Earth's magnetosphere to never come back to Earth.

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