Publications
282 results found
Gingell I, Schwartz SJ, Eastwood JP, et al., 2019, Observations of magnetic reconnection in the ransition region of quasi-parallel hocks, Geophysical Research Letters, Vol: 46, Pages: 1177-1184, ISSN: 0094-8276
Using observations of Earth's bow shock by the Magnetospheric Multiscale mission, we show for the first time that active magnetic reconnection is occurring at current sheets embedded within the quasi‐parallel shock's transition layer. We observe an electron jet and heating but no ion response, suggesting we have observed an electron‐only mode. The lack of ion response is consistent with simulations showing reconnection onset on sub‐ion time scales. We also discuss the impact of electron heating in shocks via reconnection.
Johlander A, Vaivads A, Khotyaintsev YV, et al., 2018, Shock ripples observed by the MMS spacecraft: ion reflection and dispersive properties, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 60, ISSN: 0741-3335
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- Citations: 21
Schwartz SJ, Avanov L, Turner D, et al., 2018, Ion kinetics in a hot flow anomaly: MMS observations, Geophysical Research Letters, Vol: 45, Pages: 11520-11529, ISSN: 0094-8276
Hot Flow Anomalies (HFAs) are transients observed at planetary bow shocks, formed by the shock interaction with a convected interplanetary current sheet. The primary interpretation relies on reflected ions channeled upstream along the current sheet. The short duration of HFAs has made direct observations of this process difficult. We employ high resolution measurements by NASA's Magnetospheric Multiscale Mission to probe the ion microphysics within a HFA. Magnetospheric Multiscale Mission data reveal a smoothly varying internal density and pressure, which increase toward the trailing edge of the HFA, sweeping up particles trapped within the current sheet. We find remnants of reflected or other backstreaming ions traveling along the current sheet, but most of these are not fast enough to out-run the incident current sheet convection. Despite the high level of internal turbulence, incident and backstreaming ions appear to couple gyro-kinetically in a coherent manner.
Goodrich KA, Ergun R, Schwartz SJ, et al., 2018, MMS Observations of Electrostatic Waves in an Oblique Shock Crossing, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 123, Pages: 9430-9442, ISSN: 2169-9380
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- Citations: 53
Bandyopadhyay R, Chasapis A, Chhiber R, et al., 2018, Solar Wind Turbulence Studies Using MMS Fast Plasma Investigation Data, ASTROPHYSICAL JOURNAL, Vol: 866, ISSN: 0004-637X
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- Citations: 44
Turner DL, Wilson LB, Liu TZ, et al., 2018, Autogenous and efficient acceleration of energetic ions upstream of Earth's bow shock, NATURE, Vol: 561, Pages: 206-+, ISSN: 0028-0836
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- Citations: 43
Gingell IL, Schwartz SJ, Gershman DJ, et al., 2018, Production of negative hydrogen ions within MMS Fast Plasma Investigation due to solar wind bombardment, Journal of Geophysical Research: Space Physics, Vol: 123, Pages: 6161-6170, ISSN: 2169-9380
The particle data delivered by Fast Plasma Investigation (FPI) instrument aboard NASA's Magnetospheric Multiscale (MMS) mission allows for exceptionally high-resolution examination of the electron and ion phase space in the near-Earth plasma environment. It is necessary to identify populations which originate from instrumental effects. Using FPI's Dual Electron Spectrometers (DES) we isolate a high energy (~keV) beam, present while the spacecraft are in the solar wind, which exhibits an azimuthal drift with period associated with the spacecraft spin. We show that this population is consistent with negative hydrogen ions H- generated by a double charge exchange interaction between the incident solar wind H+ ions and the metallic surfaces within the instrument. This interaction is likely to occur at the deflector plates close to the instrument aperture. The H- density is shown to be approximately 0.2-0.4% of the solar wind ion density, and the energy of the negative ion population is shown to be 70% of the incident solar wind energy. These negative ions may introduce errors in electron velocity moments on the order of 0.2-0.4% of the solar wind velocity, and significantly higher errors in the electron temperature.
Chen L-J, Wang S, Wilson LB, et al., 2018, Electron Bulk Acceleration and Thermalization at Earth's Quasiperpendicular Bow Shock., Phys Rev Lett, Vol: 120
Electron heating at Earth's quasiperpendicular bow shock has been surmised to be due to the combined effects of a quasistatic electric potential and scattering through wave-particle interaction. Here we report the observation of electron distribution functions indicating a new electron heating process occurring at the leading edge of the shock front. Incident solar wind electrons are accelerated parallel to the magnetic field toward downstream, reaching an electron-ion relative drift speed exceeding the electron thermal speed. The bulk acceleration is associated with an electric field pulse embedded in a whistler-mode wave. The high electron-ion relative drift is relaxed primarily through a nonlinear current-driven instability. The relaxed distributions contain a beam traveling toward the shock as a remnant of the accelerated electrons. Similar distribution functions prevail throughout the shock transition layer, suggesting that the observed acceleration and thermalization is essential to the cross-shock electron heating.
Eastwood J, Mistry R, Phan TD, et al., 2018, Guide field reconnection: exhaust structure and heating, Geophysical Research Letters, Vol: 45, Pages: 4569-4577, ISSN: 0094-8276
Magnetospheric Multiscale (MMS) observations are used to probe the structure and temperature profile of a guide field reconnection exhaust ~100 ion inertial lengths downstream from the X‐line in the Earth's magnetosheath. Asymmetric Hall electric and magnetic field signatures were detected, together with a density cavity confined near one edge of the exhaust and containing electron flow toward the X‐line. Electron holes were also detected both on the cavity edge and at the Hall magnetic field reversal. Predominantly parallel ion and electron heating was observed in the main exhaust but within the cavity, electron cooling and enhanced parallel ion heating was found. This is explained in terms of the parallel electric field, which inhibits electron mixing within the cavity on newly reconnected field lines, but accelerates ions. Consequently, guide field reconnection causes inhomogeneous changes in ion and electron temperature across the exhaust.
Ergun RE, Goodrich KA, Wilder FD, et al., 2018, Magnetic Reconnection, Turbulence, and Particle Acceleration: Observations in the Earth's Magnetotail, Geophysical Research Letters, Vol: 45, Pages: 3338-3347, ISSN: 0094-8276
We report observations of turbulent dissipation and particle acceleration from large-amplitude electric fields (E) associated with strong magnetic field (B) fluctuations in the Earth's plasma sheet. The turbulence occurs in a region of depleted density with anti-earthward flows followed by earthward flows suggesting ongoing magnetic reconnection. In the turbulent region, ions and electrons have a significant increase in energy, occasionally > 100 keV, and strong variation. There are numerous occurrences of |E| > 100 mV/m including occurrences of large potentials ( > 1 kV) parallel to B and occurrences with extraordinarily large J · E (J is current density). In this event, we find that the perpendicular contribution of J · E with frequencies near or below the ion cyclotron frequency (f ci ) provide the majority net positive J · E. Large-amplitude parallel E events with frequencies above f ci to several times the lower hybrid frequency provide significant dissipation and can result in energetic electron acceleration.
Gershman DJ, F-Vinas A, Dorelli JC, et al., 2018, Energy partitioning constraints at kinetic scales in low-beta turbulence, PHYSICS OF PLASMAS, Vol: 25, ISSN: 1070-664X
Broll JM, Fuselier SA, Trattner KJ, et al., 2018, MMS Observation of Shock-Reflected He<SUP>++</SUP> at Earth's Quasi-Perpendicular Bow Shock, GEOPHYSICAL RESEARCH LETTERS, Vol: 45, Pages: 49-55, ISSN: 0094-8276
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- Citations: 7
Mejnertsen L, Eastwood J, Hietala H, et al., 2017, Global MHD simulations of the Earth's bow shock shape and motion under variable solar wind conditions, Journal of Geophysical Research: Space Physics, Vol: 123, Pages: 259-271, ISSN: 2169-9380
Empirical models of the Earth's bow shock are often used to place in situ measurements in context and to understand the global behavior of the foreshock/bow shock system. They are derived statistically from spacecraft bow shock crossings and typically treat the shock surface as a conic section parameterized according to a uniform solar wind ram pressure, although more complex models exist. Here a global magnetohydrodynamic simulation is used to analyze the variability of the Earth's bow shock under real solar wind conditions. The shape and location of the bow shock is found as a function of time, and this is used to calculate the shock velocity over the shock surface. The results are compared to existing empirical models. Good agreement is found in the variability of the subsolar shock location. However, empirical models fail to reproduce the two-dimensional shape of the shock in the simulation. This is because significant solar wind variability occurs on timescales less than the transit time of a single solar wind phase front over the curved shock surface. Empirical models must therefore be used with care when interpreting spacecraft data, especially when observations are made far from the Sun-Earth line. Further analysis reveals a bias to higher shock speeds when measured by virtual spacecraft. This is attributed to the fact that the spacecraft only observes the shock when it is in motion. This must be accounted for when studying bow shock motion and variability with spacecraft data.
Gingell IL, Schwartz SJ, Burgess D, et al., 2017, MMS observations and hybrid simulations of surface ripples at a marginally quasi-parallel shock, Journal of Geophysical Research: Space Physics, Vol: 122, Pages: 11003-11017, ISSN: 2169-9380
Simulations and observations of collisionless shocks have shown that deviations of the nominal local shock normal orientation, i.e. surface waves or ripples, are expected to propagate in the ramp and overshoot of quasi-perpendicular shocks. Here, we identify signatures of a surface ripple propagating during a crossing of Earth's marginally quasi-parallel (θBn∼45∘) or quasi-parallel bow shock shock on 2015-11-27 06:01:44 UTC by the Magnetospheric Multiscale (MMS) mission, and determine the ripple's properties using multi-spacecraft methods. Using two-dimensional hybrid simulations, we confirm that surface ripples are a feature of marginally quasi-parallel and quasi-parallel shocks under the observed solar wind conditions. In addition, since these marginally quasi-parallel and quasi-parallel shocks are expected to undergo a cyclic reformation of the shock front, we discuss the impact of multiple sources of non-stationarity on shock structure. Importantly, ripples are shown to be transient phenomena, developing faster than an ion gyroperiod and only during the period of the reformation cycle when a newly developed shock ramp is unaffected by turbulence in the foot. We conclude that the change in properties of the ripple observed by MMS is consistent with the reformation of the shock front over a timescale of an ion gyro-period.
Westphal A, Riedl KM, Cooperstone JL, et al., 2017, High-Pressure Processing of Broccoli Sprouts: Influence on Bioactivation of Glucosinolates to Isothiocyanates, JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY, Vol: 65, Pages: 8578-8585, ISSN: 0021-8561
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- Citations: 39
Wilder FD, Ergun RE, Newman DL, et al., 2017, The nonlinear behavior of whistler waves at the reconnecting dayside magnetopause as observed by the Magnetospheric Multiscale mission: A case study, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 122, Pages: 5487-5501, ISSN: 2169-9380
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- Citations: 21
Yan B, Martinez-Monteagudo SI, Cooperstone JL, et al., 2017, Impact of Thermal and Pressure-Based Technologies on Carotenoid Retention and Quality Attributes in Tomato Juice, FOOD AND BIOPROCESS TECHNOLOGY, Vol: 10, Pages: 808-818, ISSN: 1935-5130
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- Citations: 25
Ergun RE, Chen L-J, Wilder FD, et al., 2017, Drift waves, intense parallel electric fields, and turbulence associated with asymmetric magnetic reconnection at the magnetopause, GEOPHYSICAL RESEARCH LETTERS, Vol: 44, Pages: 2978-2986, ISSN: 0094-8276
Observations of magnetic reconnection at Earth's magnetopause often display asymmetric structures that are accompanied by strong magnetic field (B) fluctuations and large-amplitude parallel electric fields (E||). The B turbulence is most intense at frequencies above the ion cyclotron frequency and below the lower hybrid frequency. The B fluctuations are consistent with a thin, oscillating current sheet that is corrugated along the electron flow direction (along the X line), which is a type of electromagnetic drift wave. Near the X line, electron flow is primarily due to a Hall electric field, which diverts ion flow in asymmetric reconnection and accompanies the instability. Importantly, the drift waves appear to drive strong parallel currents which, in turn, generate large-amplitude (~100 mV/m) E|| in the form of nonlinear waves and structures. These observations suggest that turbulence may be common in asymmetric reconnection, penetrate into the electron diffusion region, and possibly influence the magnetic reconnection process.
Gershman DJ, F-Vinas A, Dorelli JC, et al., 2017, Wave-particle energy exchange directly observed in a kinetic Alfven-branch wave, NATURE COMMUNICATIONS, Vol: 8, ISSN: 2041-1723
Alfvén waves are fundamental plasma wave modes that permeate the universe. At small kinetic scales, they provide a critical mechanism for the transfer of energy between electromagnetic fields and charged particles. These waves are important not only in planetary magnetospheres, heliospheres and astrophysical systems but also in laboratory plasma experiments and fusion reactors. Through measurement of charged particles and electromagnetic fields with NASA’s Magnetospheric Multiscale (MMS) mission, we utilize Earth’s magnetosphere as a plasma physics laboratory. Here we confirm the conservative energy exchange between the electromagnetic field fluctuations and the charged particles that comprise an undamped kinetic Alfvén wave. Electrons confined between adjacent wave peaks may have contributed to saturation of damping effects via nonlinear particle trapping. The investigation of these detailed wave dynamics has been unexplored territory in experimental plasma physics and is only recently enabled by high-resolution MMS observations.
Stawarz JE, Eriksson S, Wilder FD, et al., 2016, Observations of turbulence in a Kelvin-Helmholtz event on September 8, 2015 by the Magnetospheric Multiscale Mission, Journal of Geophysical Research: Space Physics, Vol: 121, Pages: 11021-11034, ISSN: 2169-9380
Spatial and high-time-resolution properties of the velocities,magnetic eld, and 3D electric eld within plasma turbulence are examined observationally using data from the Magnetospheric Multiscale Mission. Observations from a Kelvin-Helmholtz instability (KHI) on the Earth's magnetopause are examined, which both provides a series of repeatable intervals to analyze, giving better statistics, and provides a rst look at the properties of turbulence in the KHI. For the rst time direct observations of both the high-frequency ion and electron velocity spectra are examined, showing differing ion and electron behavior at kinetic scales. Temporal spectra ex-hibit power law behavior with changes in slope near the ion gyrofrequency and lower-hybrid frequency. The work provides the rst observational evi-dence for turbulent intermittency and anisotropy consistent with quasi-two-dimensional turbulence in association with the KHI. The behavior of kinetic scale intermittency is found to have di erences from previous studies of solar wind turbulence, leading to novel insights on the turbulent dynamics inthe KHI.
Galand M, Héritier KL, Odelstad E, et al., 2016, Ionospheric plasma of comet 67P probed by Rosetta at 3 AU from the Sun, Monthly Notices of the Royal Astronomical Society, Vol: 462, Pages: S331-S351, ISSN: 1365-2966
We propose to identify the main sources of ionization of the plasma in the coma of comet 67P/Churyumov–Gerasimenko at different locations in the coma and to quantify their relative importance, for the first time, for close cometocentric distances (<20 km) and large heliocentric distances (>3 au). The ionospheric model proposed is used as an organizing element of a multi-instrument data set from the Rosetta Plasma Consortium (RPC) plasma and particle sensors, from the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis and from the Microwave Instrument on the Rosetta Orbiter, all on board the ESA/Rosetta spacecraft. The calculated ionospheric density driven by Rosetta observations is compared to the RPC-Langmuir Probe and RPC-Mutual Impedance Probe electron density. The main cometary plasma sources identified are photoionization of solar extreme ultraviolet (EUV) radiation and energetic electron-impact ionization. Over the northern, summer hemisphere, the solar EUV radiation is found to drive the electron density – with occasional periods when energetic electrons are also significant. Over the southern, winter hemisphere, photoionization alone cannot explain the observed electron density, which reaches sometimes higher values than over the summer hemisphere; electron-impact ionization has to be taken into account. The bulk of the electron population is warm with temperature of the order of 7–10 eV. For increased neutral densities, we show evidence of partial energy degradation of the hot electron energy tail and cooling of the full electron population
Johlander A, Schwartz SJ, Vaivads A, et al., 2016, Rippled Quasiperpendicular Shock Observed by the Magnetospheric Multiscale Spacecraft, Physical Review Letters, Vol: 117, ISSN: 1079-7114
Collisionless shock nonstationarity arising from microscale physics influences shock structure andparticle acceleration mechanisms. Nonstationarity has been difficult to quantify due to the small spatial andtemporal scales. We use the closely spaced (subgyroscale), high-time-resolution measurements from onerapid crossing of Earth’s quasiperpendicular bow shock by the Magnetospheric Multiscale (MMS)spacecraft to compare competing nonstationarity processes. Using MMS’s high-cadence kinetic plasmameasurements, we show that the shock exhibits nonstationarity in the form of ripples.
Wilder FD, Ergun RE, Schwartz SJ, et al., 2016, Observations of large-amplitude, parallel, electrostatic waves associated with the Kelvin-Helmholtz instability by the magnetospheric multiscale mission, Geophysical Research Letters, Vol: 43, Pages: 8859-8866, ISSN: 1944-8007
On 8 September 2015, the four Magnetospheric Multiscale spacecraft encountered a Kelvin-Helmholtz unstable magnetopause near the dusk flank. The spacecraft observed periodic compressed current sheets, between which the plasma was turbulent. We present observations of large-amplitude (up to 100 mV/m) oscillations in the electric field. Because these oscillations are purely parallel to the background magnetic field, electrostatic, and below the ion plasma frequency, they are likely to be ion acoustic-like waves. These waves are observed in a turbulent plasma where multiple particle populations are intermittently mixed, including cold electrons with energies less than 10 eV. Stability analysis suggests a cold electron component is necessary for wave growth.
Broiles TW, Livadiotis G, Burch JL, et al., 2016, Characterizing cometary electrons with kappa distributions, Journal of Geophysical Research. Solid Earth, Vol: 121, Pages: 7407-7422, ISSN: 2169-9356
The Rosetta spacecraft has escorted comet 67P/Churyumov-Gerasimenko since 6 August 2014and has offered an unprecedented opportunity to study plasma physics in the coma. We have usedthis opportunity to make thefirst characterization of cometary electrons with kappa distributions. Twothree-dimensional kappa functions werefit to the observations, which we interpret as two populations ofdense and warm (density=10cm3, temperature=2×105K, invariant kappa index=10>1000), andrarefied and hot (density=0.005cm3, temperature=5×105K, invariant kappa index=1–10) electrons. Wefit the observations on 30 October 2014 when Rosetta was 20km from 67P, and 3AU from the Sun. Werepeated the analysis on 15 August 2015 when Rosetta was 300km from the comet and 1.3AU from the Sun.Comparing the measurements on both days gives thefirst comparison of the cometary electron environmentbetween a nearly inactive comet far from the Sun and an active comet near perihelion. Wefind that the warmpopulation density increased by a factor of 3, while the temperature cooled by a factor of 2, and the invariantkappa index was unaffected. Wefind that the hot population density increased by a factor of 10, whilethe temperature and invariant kappa index were unchanged. We conclude that the hot population islikely the solar wind halo electrons in the coma. The warm population is likely of cometary origin, but itsmechanism for production is not known.
Eriksson S, Wilder FD, Ergun RE, et al., 2016, Magnetospheric Multiscale Observations of the Electron Diffusion Region of Large Guide Field Magnetic Reconnection, Physical Review Letters, Vol: 117, ISSN: 1079-7114
We report observations from the Magnetospheric Multiscale (MMS) satellites of a large guide field magnetic reconnection event. The observations suggest that two of the four MMS spacecraft sampled the electron diffusion region, whereas the other two spacecraft detected the exhaust jet from the event. The guide magnetic field amplitude is approximately 4 times that of the reconnecting field. The event is accompanied by a significant parallel electric field (E∥) that is larger than predicted by simulations. The high-speed (∼300 km/s) crossing of the electron diffusion region limited the data set to one complete electron distribution inside of the electron diffusion region, which shows significant parallel heating. The data suggest that E∥ is balanced by a combination of electron inertia and a parallel gradient of the gyrotropic electron pressure.
Ergun RE, Goodrich KA, Wilder FD, et al., 2016, Magnetospheric multiscale satellites observations of parallel electric fields associated with magnetic reconnection, Physical Review Letters, Vol: 116, ISSN: 1079-7114
We report observations from the Magnetospheric Multiscale satellites of parallel electric fields (E_{∥}) associated with magnetic reconnection in the subsolar region of the Earth's magnetopause. E_{∥} events near the electron diffusion region have amplitudes on the order of 100 mV/m, which are significantly larger than those predicted for an antiparallel reconnection electric field. This Letter addresses specific types of E_{∥} events, which appear as large-amplitude, near unipolar spikes that are associated with tangled, reconnected magnetic fields. These E_{∥} events are primarily in or near a current layer near the separatrix and are interpreted to be double layers that may be responsible for secondary reconnection in tangled magnetic fields or flux ropes. These results are telling of the three-dimensional nature of magnetopause reconnection and indicate that magnetopause reconnection may be often patchy and/or drive turbulence along the separatrix that results in flux ropes and/or tangled magnetic fields.
Eriksson S, Lavraud B, Wilder FD, et al., 2016, Magnetospheric Multiscale observations of magnetic reconnection associated with Kelvin-Helmholtz waves, Geophysical Research Letters, Vol: 43, Pages: 5606-5615, ISSN: 1944-8007
The four Magnetospheric Multiscale (MMS) spacecraft recorded the first direct evidence of reconnection exhausts associated with Kelvin-Helmholtz (KH) waves at the duskside magnetopause on 8 September 2015 which allows for local mass and energy transport across the flank magnetopause. Pressure anisotropy-weighted Walén analyses confirmed in-plane exhausts across 22 of 42 KH-related trailing magnetopause current sheets (CSs). Twenty-one jets were observed by all spacecraft, with small variations in ion velocity, along the same sunward or antisunward direction with nearly equal probability. One exhaust was only observed by the MMS-1,2 pair, while MMS-3,4 traversed a narrow CS (1.5 ion inertial length) in the vicinity of an electron diffusion region. The exhausts were locally 2-D planar in nature as MMS-1,2 observed almost identical signatures separated along the guide-field. Asymmetric magnetic and electric Hall fields are reported in agreement with a strong guide-field and a weak plasma density asymmetry across the magnetopause CS.
Wilder FD, Ergun RE, Goodrich KA, et al., 2016, Observations of whistler mode waves with nonlinear parallel electric fields near the dayside magnetic reconnection separatrix by the Magnetospheric Multiscale mission, Geophysical Research Letters, Vol: 43, Pages: 5909-5917, ISSN: 1944-8007
We show observations from the Magnetospheric Multiscale (MMS) mission of whistler mode waves in the Earth's low-latitude boundary layer (LLBL) during a magnetic reconnection event. The waves propagated obliquely to the magnetic field toward the X line and were confined to the edge of a southward jet in the LLBL. Bipolar parallel electric fields interpreted as electrostatic solitary waves (ESW) are observed intermittently and appear to be in phase with the parallel component of the whistler oscillations. The polarity of the ESWs suggests that if they propagate with the waves, they are electron enhancements as opposed to electron holes. The reduced electron distribution shows a shoulder in the distribution for parallel velocities between 17,000 and 22,000 km/s, which persisted during the interval when ESWs were observed, and is near the phase velocity of the whistlers. This shoulder can drive Langmuir waves, which were observed in the high-frequency parallel electric field data.
Ergun RE, Holmes JC, Goodrich KA, et al., 2016, Magnetospheric Multiscale observations of large-amplitude, parallel, electrostatic waves associated with magnetic reconnection at the magnetopause, Geophysical Research Letters, Vol: 43, Pages: 5626-5634, ISSN: 0094-8276
We report observations from the Magnetospheric Multiscale satellites of large-amplitude, parallel, electrostatic waves associated with magnetic reconnection at the Earth's magnetopause. The observed waves have parallel electric fields (E||) with amplitudes on the order of 100 mV/m and display nonlinear characteristics that suggest a possible net E||. These waves are observed within the ion diffusion region and adjacent to (within several electron skin depths) the electron diffusion region. They are in or near the magnetosphere side current layer. Simulation results support that the strong electrostatic linear and nonlinear wave activities appear to be driven by a two stream instability, which is a consequence of mixing cold (<10 eV) plasma in the magnetosphere with warm (~100 eV) plasma from the magnetosheath on a freshly reconnected magnetic field line. The frequent observation of these waves suggests that cold plasma is often present near the magnetopause.
Lavraud B, Zhang YC, Vernisse Y, et al., 2016, Currents and associated electron scattering and bouncing near the diffusion region at Earth's magnetopause, Geophysical Research Letters, Vol: 43, Pages: 3042-3050, ISSN: 1944-8007
Based on high-resolution measurements from NASA's Magnetospheric Multiscale mission, we present the dynamics of electrons associated with current systems observed near the diffusion region of magnetic reconnection at Earth's magnetopause. Using pitch angle distributions (PAD) and magnetic curvature analysis, we demonstrate the occurrence of electron scattering in the curved magnetic field of the diffusion region down to energies of 20eV. We show that scattering occurs closer to the current sheet as the electron energy decreases. The scattering of inflowing electrons, associated with field-aligned electrostatic potentials and Hall currents, produces a new population of scattered electrons with broader PAD which bounce back and forth in the exhaust. Except at the center of the diffusion region the two populations are collocated and appear to behave adiabatically: the inflowing electron PAD focuses inward (toward lower magnetic field), while the bouncing population PAD gradually peaks at 90° away from the center (where it mirrors owing to higher magnetic field and probable field-aligned potentials).
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