| 1. |
- Nakamura, R., et al.
(författare)
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Transient, small-scale field-aligned currents in the plasma sheet boundary layer during storm time substorms
- 2016
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 43:10, s. 4841-4849
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Tidskriftsartikel (refereegranskat)abstract
- We report on field-aligned current observations by the four Magnetospheric Multiscale (MMS) spacecraft near the plasma sheet boundary layer (PSBL) during two major substorms on 23 June 2015. Small-scale field-aligned currents were found embedded in fluctuating PSBL flux tubes near the separatrix region. We resolve, for the first time, short-lived earthward (downward) intense field-aligned current sheets with thicknesses of a few tens of kilometers, which are well below the ion scale, on flux tubes moving equatorward/earthward during outward plasma sheet expansion. They coincide with upward field-aligned electron beams with energies of a few hundred eV. These electrons are most likely due to acceleration associated with a reconnection jet or high-energy ion beam-produced disturbances. The observations highlight coupling of multiscale processes in PSBL as a consequence of magnetotail reconnection.
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| 2. |
- Burch, J. L., et al.
(författare)
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High-Frequency Wave Generation in Magnetotail Reconnection : Linear Dispersion Analysis
- 2019
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Ingår i: Geophysical Research Letters. - : AMER GEOPHYSICAL UNION. - 0094-8276 .- 1944-8007. ; 46:8, s. 4089-4097
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Tidskriftsartikel (refereegranskat)abstract
- Plasma and wave measurements from the NASA Magnetospheric Multiscale mission are presented for magnetotail reconnection events on 3 July and 11 July 2017. Linear dispersion analyses were performed using distribution functions comprising up to six drifting bi-Maxwellian distributions. In both events electron crescent-shaped distributions are shown to be responsible for upper hybrid waves near the X-line. In an adjacent location within the 3 July event a monodirectional field-aligned electron beam drove parallel-propagating beam-mode waves. In the 11 July event an electron distribution consisting of a drifting core and two crescents was shown to generate upper-hybrid and beam-mode waves at three different frequencies, explaining the observed broadband waves. Multiple harmonics of the upper hybrid waves were observed but cannot be explained by the linear dispersion analysis since they result from nonlinear beam interactions. Plain Language Summary Magnetic reconnection is a process that occurs throughout the universe in ionized gases (plasmas) containing embedded magnetic fields. This process converts magnetic energy to electron and ion energy, causing phenomena such as solar flares and auroras. The NASA Magnetospheric Multiscale mission has shown that in magnetic reconnection regions there are intense electric field oscillations or waves and that electrons form crescent and beam-like populations propagating both along and perpendicular to the magnetic field. This study shows that the observed electron populations are responsible for high-frequency waves including their propagation directions and frequency ranges.
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| 3. |
- Genestreti, K. J., et al.
(författare)
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MMS Observation of Asymmetric Reconnection Supported by 3-D Electron Pressure Divergence
- 2018
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Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 123:3, s. 1806-1821
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Tidskriftsartikel (refereegranskat)abstract
- We identify the electron diffusion region (EDR) of a guide field dayside reconnection site encountered by the Magnetospheric Multiscale (MMS) mission and estimate the terms in generalized Ohm's law that controlled energy conversion near the X-point. MMS crossed the moderate-shear (similar to 130 degrees) magnetopause southward of the exact X-point. MMS likely entered the magnetopause far from the X-point, outside the EDR, as the size of the reconnection layer was less than but comparable to the magnetosheath proton gyroradius, and also as anisotropic gyrotropic "outflow" crescent electron distributions were observed. MMS then approached the X-point, where all four spacecraft simultaneously observed signatures of the EDR, for example, an intense out-of-plane electron current, moderate electron agyrotropy, intense electron anisotropy, nonideal electric fields, and nonideal energy conversion. We find that the electric field associated with the nonideal energy conversion is (a) well described by the sum of the electron inertial and pressure divergence terms in generalized Ohms law though (b) the pressure divergence term dominates the inertial term by roughly a factor of 5:1, (c) both the gyrotropic and agyrotropic pressure forces contribute to energy conversion at the X-point, and (d) both out-of-the-reconnection-plane gradients (partial derivative/partial derivative M) and in-plane (partial derivative/partial derivative L, N) in the pressure tensor contribute to energy conversion near the X-point. This indicates that this EDR had some electron-scale structure in the out-of-plane direction during the time when (and at the location where) the reconnection site was observed.
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| 4. |
- Hasegawa, H., et al.
(författare)
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Magnetic Field Annihilation in a Magnetotail Electron Diffusion Region With Electron-Scale Magnetic Island
- 2022
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Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 127:7
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Tidskriftsartikel (refereegranskat)abstract
- We present observations in Earth's magnetotail by the Magnetospheric Multiscale spacecraft that are consistent with magnetic field annihilation, rather than magnetic topology change, causing fast magnetic-to-electron energy conversion in an electron-scale current sheet. Multi-spacecraft analysis for the magnetic field reconstruction shows that an electron-scale magnetic island was embedded in the observed electron diffusion region (EDR), suggesting an elongated shape of the EDR. Evidence for the annihilation was revealed in the form of the island growing at a rate much lower than expected for the standard X-type geometry of the EDR, which indicates that magnetic flux injected into the EDR was not ejected from the X-point or accumulated in the island, but was dissipated in the EDR. This energy conversion process is in contrast to that in the standard EDR of a reconnecting current sheet where the energy of antiparallel magnetic fields is mostly converted to electron bulk-flow energy. Fully kinetic simulation also demonstrates that an elongated EDR is subject to the formation of electron-scale magnetic islands in which fast but transient annihilation can occur. Consistent with the observations and simulation, theoretical analysis shows that fast magnetic diffusion can occur in an elongated EDR in the presence of nongyrotropic electron effects. We suggest that the annihilation in elongated EDRs may contribute to the dissipation of magnetic energy in a turbulent collisionless plasma.
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| 5. |
- Hasegawa, H., et al.
(författare)
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Reconstruction of the Electron Diffusion Region of Magnetotail Reconnection seen by the MMS Spacecraft on 11July 2017
- 2019
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 124:1, s. 122-138
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Tidskriftsartikel (refereegranskat)abstract
- We present results from the reconstruction of the electron diffusion region of magnetotail reconnection observed by the Magnetospheric Multiscale (MMS) spacecraft on 11 July 2017. In the event, the conditions were suited for the reconstruction technique, developed by Sonnerup et al. (2016, https://doi.org/10.1002/2016JA022430), that produces magnetic field and electron streamline maps based on a two-dimensional, time-independent, inertialess form of electron magnetohydrodynamic equation, assuming an approximately symmetric current sheet and negligible guide magnetic field. For such a two-dimensional and steady structure, the X line orientation can be estimated from a method based on Ampere's law using single-spacecraft measurements of the magnetic field and electric current density. Our reconstruction results indicate that although the X point was not captured inside its tetrahedron, MMS approached the X point as close as one electron inertial length similar to 27 km. The opening angle of the recovered separatrix field line, combined with theory, suggests that the dimensionless reconnection rate was 0.17, which is consistent with the measured reconnection electric field 2-4 mV/m. The stagnation point of the reconstructed electron flow is shifted earthward of the X point by similar to 90 km, one possible interpretation of which is discussed. The energy conversion rate j . E' in the electron frame tends to be higher near the stagnation point, consistent with earlier observations and simulations, and is not correlated with the amplitude of broadband electrostatic waves observed in the upper-hybrid frequency range. The latter suggests that the waves did not contribute to energy dissipation in this particular electron diffusion region. Plain Language Summary Magnetic reconnection is a fundamental plasma process that controls transfer of solar wind energy and mass to planetary magnetospheres and causes explosive energy release associated with solar flares and sudden auroral brightening. National Aeronautics and Space Administration's Magnetospheric Multiscale (MMS) mission, which consists of four identical spacecraft launched in March 2015, aims at elucidating how magnetic reconnection works with unprecedented high temporal and spatial resolution measurements of charged particles and electromagnetic fields in space. MMS has been observing the Earth's magnetotail since May 2017 and encountered the central region of magnetic reconnection, called the electron diffusion region, on 11 July 2017. In this study, we present two-dimensional images of this region recovered from the MMS electron and magnetic field measurements, showing that the electron flow pattern in the electron diffusion region is not as simple as predicted by theory. The results provide new insights about the reconnection process in the actual space environment.
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| 6. |
- Burch, J. L., et al.
(författare)
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Localized Oscillatory Energy Conversion in Magnetopause Reconnection
- 2018
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Ingår i: Geophysical Research Letters. - : AMER GEOPHYSICAL UNION. - 0094-8276 .- 1944-8007. ; 45:3, s. 1237-1245
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Tidskriftsartikel (refereegranskat)abstract
- Data from the NASA Magnetospheric Multiscale mission are used to investigate asymmetric magnetic reconnection at the dayside boundary between the Earth's magnetosphere and the solar wind. High-resolution measurements of plasmas and fields are used to identify highly localized (similar to 15 electron Debye lengths) standing wave structures with large electric field amplitudes (up to 100 mV/m). These wave structures are associated with spatially oscillatory energy conversion, which appears as alternatingly positive and negative values of J . E. For small guide magnetic fields the wave structures occur in the electron stagnation region at the magnetosphere edge of the electron diffusion region. For larger guide fields the structures also occur near the reconnection X-line. This difference is explained in terms of channels for the out-of-plane current (agyrotropic electrons at the stagnation point and guide field-aligned electrons at the X-line).
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| 7. |
- Burch, J. L., et al.
(författare)
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Wave Phenomena and Beam-Plasma Interactions at the Magnetopause Reconnection Region
- 2018
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 123:2, s. 1118-1133
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on Magnetospheric Multiscale observations of whistler mode chorus and higher-frequency electrostatic waves near and within a reconnection diffusion region on 23 November 2016. The diffusion region is bounded by crescent-shaped electron distributions and associated dissipation just upstream of the X-line and by magnetic field-aligned currents and electric fields leading to dissipation near the electron stagnation point. Measurements were made southward of the X-line as determined by southward directed ion and electron jets. We show that electrostatic wave generation is due to magnetosheath electron beams formed by the electron jets as they interact with a cold background plasma and more energetic population of magnetospheric electrons. On the magnetosphere side of the X-line the electron beams are accompanied by a strong perpendicular electron temperature anisotropy, which is shown to be the source of an observed rising-tone whistler mode chorus event. We show that the apex of the chorus event and the onset of electrostatic waves coincide with the opening of magnetic field lines at the electron stagnation point.
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| 8. |
- Ergun, R. E., et al.
(författare)
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Magnetic Reconnection, Turbulence, and Particle Acceleration : Observations in the Earth's Magnetotail
- 2018
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Ingår i: Geophysical Research Letters. - : Blackwell Publishing Ltd. - 0094-8276 .- 1944-8007. ; 45:8, s. 3338-3347
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Tidskriftsartikel (refereegranskat)abstract
- 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 (fci) provide the majority net positive J · E. Large-amplitude parallel E events with frequencies above fci to several times the lower hybrid frequency provide significant dissipation and can result in energetic electron acceleration.
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| 9. |
- Nakamura, T. K. M., et al.
(författare)
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Mass and Energy Transfer Across the Earth's Magnetopause Caused by Vortex-Induced Reconnection
- 2017
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Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 122:11, s. 11505-11522
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Tidskriftsartikel (refereegranskat)abstract
- When the interplanetary magnetic field (IMF) is strongly northward, a boundary layer that contains a considerable amount of plasma of magnetosheath origin is often observed along and earthward of the low-latitude magnetopause. Such a preexisting boundary layer, with a higher density than observed in the adjacent magnetosphere, reduces the local Alfven speed and allows the Kelvin-Helmholtz (KH) instability to grow more strongly. We employ a three-dimensional fully kinetic simulation to model an event observed by the Magnetospheric Multiscale (MMS) mission in which the spacecraft detected substantial KH waves between a preexisting boundary layer and the magnetosheath during strong northward IMF. Initial results of this simulation have successfully demonstrated ion-scale signatures of magnetic reconnection induced by the nonlinearly developed KH vortex, which are quantitatively consistent with MMS observations. We further quantify the simulated mass and energy transfer processes driven by this vortex-induced reconnection (VIR) and show that during this particular MMS event, (i) mass enters a new mixing layer formed by the VIR more efficiently from the preexisting boundary layer side than from the magnetosheath side, (ii) mixed plasmas within the new mixing layer convect tailward along the magnetopause at more than half the magnetosheath flow speed, and (iii) energy dissipation in localized VIR dissipation regions results in a strong parallel electron heating within the mixing layer. The quantitative agreements between the simulation and MMS observations allow new predictions that elucidate how the mass and energy transfer processes occur near the magnetopause during strong northward IMF.
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| 10. |
- Toledo-Redondo, S., et al.
(författare)
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Solar Wind-Magnetosphere Coupling During Radial Interplanetary Magnetic Field Conditions : Simultaneous Multi-Point Observations
- 2021
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Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 126:11
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Tidskriftsartikel (refereegranskat)abstract
- In-situ spacecraft missions are powerful assets to study processes that occur in space plasmas. One of their main limitations, however, is extrapolating such local measurements to the global scales of the system. To overcome this problem at least partially, multi-point measurements can be used. There are several multi-spacecraft missions currently operating in the Earth's magnetosphere, and the simultaneous use of the data collected by them provides new insights into the large-scale properties and evolution of magnetospheric plasma processes. In this work, we focus on studying the Earth's magnetopause (MP) using a conjunction between the Magnetospheric Multiscale and Cluster fleets, when both missions skimmed the MP for several hours at distant locations during radial interplanetary magnetic field (IMF) conditions. The observed MP positions as a function of the evolving solar wind conditions are compared to model predictions of the MP. We observe an inflation of the magnetosphere (similar to 0.7 R-E), consistent with magnetosheath pressure decrease during radial IMF conditions, which is less pronounced on the flank (<0.2 R-E). There is observational evidence of magnetic reconnection in the subsolar region for the whole encounter, and in the dusk flank for the last portion of the encounter, suggesting that reconnection was extending more than 15 R-E. However, reconnection jets were not always observed, suggesting that reconnection was patchy, intermittent or both. Shear flows reduce the reconnection rate up to similar to 30% in the dusk flank according to predictions, and the plasma beta enhancement in the magnetosheath during radial IMF favors reconnection suppression by the diamagnetic drift.
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| 11. |
- Torbert, R. B., et al.
(författare)
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Electron-scale dynamics of the diffusion region during symmetric magnetic reconnection in space
- 2018
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Ingår i: Science. - : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 362:6421, s. 1391-1395
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic reconnection is an energy conversion process that occurs in many astrophysical contexts including Earth's magnetosphere, where the process can be investigated in situ by spacecraft. On 11 July 2017, the four Magnetospheric Multiscale spacecraft encountered a reconnection site in Earth's magnetotail, where reconnection involves symmetric inflow conditions. The electron-scale plasma measurements revealed (i) super-Alfvenic electron jets reaching 15,000 kilometers per second; (ii) electron meandering motion and acceleration by the electric field, producing multiple crescent-shaped structures in the velocity distributions; and (iii) the spatial dimensions of the electron diffusion region with an aspect ratio of 0.1 to 0.2, consistent with fast reconnection. The well-structured multiple layers of electron populations indicate that the dominant electron dynamics are mostly laminar, despite the presence of turbulence near the reconnection site.
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| 12. |
- Varsani, A., et al.
(författare)
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Simultaneous Remote Observations of Intense Reconnection Effects by DMSP and MMS Spacecraft During a Storm Time Substorm
- 2017
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 122:11, s. 10891-10909
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Tidskriftsartikel (refereegranskat)abstract
- During a magnetic storm on 23 June 2015, several very intense substorms took place, with signatures observed by multiple spacecraft including DMSP and Magnetospheric Multiscale (MMS). At the time of interest, DMSP F18 crossed inbound through a poleward expanding auroral bulge boundary at 23.5 h magnetic local time (MLT), while MMS was located duskward of 22 h MLT during an inward crossing of the expanding plasma sheet boundary. The two spacecraft observed a consistent set of signatures as they simultaneously crossed the reconnection separatrix layer during this very intense reconnection event. These include (1) energy dispersion of the energetic ions and electrons traveling earthward, accompanied with high electron energies in the vicinity of the separatrix; (2) energy dispersion of polar rain electrons, with a high-energy cutoff; and (3) intense inward convection of the magnetic field lines at the MMS location. The high temporal resolution measurements by MMS provide unprecedented observations of the outermost electron boundary layer. We discuss the relevance of the energy dispersion of the electrons, and their pitch angle distribution, to the spatial and temporal evolution of the boundary layer. The results indicate that the underlying magnetotail magnetic reconnection process was an intrinsically impulsive and the active X-line was located relatively close to the Earth, approximately at 16-18 R-E.
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| 13. |
- Webster, J. M., et al.
(författare)
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Magnetospheric Multiscale Dayside Reconnection Electron Diffusion Region Events
- 2018
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 123:6, s. 4858-4878
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Tidskriftsartikel (refereegranskat)abstract
- We use high-resolution data from dayside passes of the Magnetospheric Multiscale (MMS) mission to create for the first time a comprehensive listing of encounters with the electron diffusion region (EDR), as evidenced by electron agyrotropy, ion jet reversals, and j.E' > 0. We present an overview of these 32 EDR or near-EDR events, which demonstrate a wide variety of observed plasma behavior inside and surrounding the reconnection site. We analyze in detail three of the 21 new EDR encounters, which occurred within a 1-min-long interval on 23 November 2016. The three events, which resulted from a relatively low and oscillating magnetopause velocity, exhibited large electric fields (up to similar to 100 mV/m), crescent-shaped electron velocity phase space densities, large currents (>= 2 mu A/m(2)), and Ohmic heating of the plasma (similar to 10 nW/m(3)). We include an Ohm's law analysis, in which we show that the divergence of the electron pressure term usually dominates the nonideal terms and is much more turbulent on the magnetosphere versus the magnetosheath side of the EDR.
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| 14. |
- Chen, L. -J, et al.
(författare)
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Electron Diffusion Regions in Magnetotail Reconnection Under Varying Guide Fields
- 2019
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Ingår i: Geophysical Research Letters. - : Blackwell Publishing. - 0094-8276 .- 1944-8007. ; 46:12, s. 6230-6238
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Tidskriftsartikel (refereegranskat)abstract
- Kinetic structures of electron diffusion regions (EDRs) under finite guide fields in magnetotail reconnection are reported. The EDRs with guide fields 0.14–0.5 (in unit of the reconnecting component) are detected by the Magnetospheric Multiscale spacecraft. The key new features include the following: (1) cold inflowing electrons accelerated along the guide field and demagnetized at the magnetic field minimum while remaining a coherent population with a low perpendicular temperature, (2) wave fluctuations generating strong perpendicular electron flows followed by alternating parallel flows inside the reconnecting current sheet under an intermediate guide field, and (3) gyrophase bunched electrons with high parallel speeds leaving the X-line region. The normalized reconnection rates for the three EDRs range from 0.05 to 0.3. The measurements reveal that finite guide fields introduce new mechanisms to break the electron frozen-in condition.
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| 15. |
- Chen, L-J, et al.
(författare)
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Lower-Hybrid Drift Waves Driving Electron Nongyrotropic Heating and Vortical Flows in a Magnetic Reconnection Layer
- 2020
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Ingår i: Physical Review Letters. - : American Physical Society (APS). - 0031-9007 .- 1079-7114. ; 125:2
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Tidskriftsartikel (refereegranskat)abstract
- We report measurements of lower-hybrid drift waves driving electron heating and vortical flows in an electron-scale reconnection layer under a guide field. Electrons accelerated by the electrostatic potential of the waves exhibit perpendicular and nongyrotropic heating. The vortical flows generate magnetic field perturbations comparable to the guide field magnitude. The measurements reveal a new regime of electron-wave interaction and how this interaction modifies the electron dynamics in the reconnection layer.
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| 16. |
- Oieroset, M., et al.
(författare)
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Spatial evolution of magnetic reconnection diffusion region structures with distance from the X-line
- 2021
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Ingår i: Physics of Plasmas. - : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 28:12
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Tidskriftsartikel (refereegranskat)abstract
- We report Magnetospheric Multiscale four-spacecraft observations of a thin reconnecting current sheet with weakly asymmetric inflow conditions and a guide field of approximately twice the reconnecting magnetic field. The event was observed at the interface of interlinked magnetic field lines at the flank magnetopause when the maximum spacecraft separation was 370 km and the spacecraft covered & SIM;1.7 ion inertial lengths (d(i)) in the reconnection outflow direction. The ion-scale spacecraft separation made it possible to observe the transition from electron-only super ion-Alfvenic outflow near the electron diffusion region (EDR) to the emergence of sub-Alfvenic ion outflow in the ion diffusion region (IDR). The EDR to IDR evolution over a distance less than 2 d(i) also shows the transition from a near-linear reconnecting magnetic field reversal to a more bifurcated current sheet as well as significant decreases in the parallel electric field and dissipation. Both the ion and electron heating in this diffusion region event were similar to the previously reported heating in the far downstream exhausts. The dimensionless reconnection rate, obtained four different ways, was in the range of 0.13-0.27. This event reveals the rapid spatial evolution of the plasma and electromagnetic fields through the EDR to IDR transition region.& nbsp;(C) 2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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| 17. |
- Stawarz, J. E., et al.
(författare)
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Intense Electric Fields and Electron-Scale Substructure Within Magnetotail Flux Ropes as Revealed by the Magnetospheric Multiscale Mission
- 2018
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 45:17, s. 8783-8792
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Tidskriftsartikel (refereegranskat)abstract
- Three flux ropes associated with near-Earth magnetotail reconnection are analyzed using Magnetospheric Multiscale observations. The flux ropes are Earthward propagating with sizes from similar to 3 to 11 ion inertial lengths. Significantly different axial orientations are observed, suggesting spatiotemporal variability in the reconnection and/or flux rope dynamics. An electron-scale vortex, associated with one of the most intense electric fields (E) in the event, is observed within one of the flux ropes. This E is predominantly perpendicular to the magnetic field (B); the electron vortex is frozen-in with E x B drifting electrons carrying perpendicular current and causing a small-scale magnetic enhancement. The vortex is similar to 16 electron gyroradii in size perpendicular to B and potentially elongated parallel to B. The need to decouple the frozen-in vortical motion from the surrounding plasma implies a parallel E at the structure's ends. The formation of frozen-in electron vortices within reconnection-generated flux ropes may have implications for particle acceleration. Plain LanguageSummary The release of magnetic energy into particle motion through magnetic reconnection is a key driver of dynamics in the Earth's magnetosphere and other space plasmas. In order to understand how the released magnetic energy is distributed and ultimately heats the particles, a detailed examination of the structures formed by magnetic reconnection is necessary. One common structure produced by reconnection is a twisted magnetic field known as a flux rope. We use new data from the National Aeronautics and Space Administration's Magnetospheric Multiscale satellites to examine both the large-and small-scale properties of three flux ropes associated with a single reconnection event. The results reveal the intrinsic three-dimensional nature of the overall reconnection event, which may stem either from variability at the reconnection site and/or the subsequent dynamics of the structures after they form. Additionally, the high-resolution measurements reveal a new small-scale structure, namely, a vortex of electrons, inside of one of the flux ropes. The presence of such vortices may contribute to accelerating particles and points to the necessity of better understanding the substructure of flux ropes in order to characterize particle energization in magnetic reconnection.
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| 18. |
- Voros, Z., et al.
(författare)
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MMS Observation of Magnetic Reconnection in the Turbulent Magnetosheath
- 2017
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 122:11, s. 11442-11467
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we use the full armament of the MMS (Magnetospheric Multiscale) spacecraft to study magnetic reconnection in the turbulent magnetosheath downstream of a quasi-parallel bow shock. Contrarily to the magnetopause and magnetotail cases, only a few observations of reconnection in the magnetosheath have been reported. The case study in this paper presents, for the first time, both fluid-scale and kinetic-scale signatures of an ongoing reconnection in the turbulent magnetosheath. The spacecraft are crossing the reconnection inflow and outflow regions and the ion diffusion region (IDR). Inside the reconnection outflows D shape ion distributions are observed. Inside the IDR mixing of ion populations, crescent-like velocity distributions and ion accelerations are observed. One of the spacecraft skims the outer region of the electron diffusion region, where parallel electric fields, energy dissipation/conversion, electron pressure tensor agyrotropy, electron temperature anisotropy, and electron accelerations are observed. Some of the difficulties of the observations of magnetic reconnection in turbulent plasma are also outlined.
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