| 1. |
- Ergun, R. E., et al.
(author)
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Magnetospheric Multiscale observations of large-amplitude, parallel, electrostatic waves associated with magnetic reconnection at the magnetopause
- 2016
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In: Geophysical Research Letters. - : Blackwell Publishing. - 0094-8276 .- 1944-8007. ; 43:11, s. 5626-5634
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Journal article (peer-reviewed)abstract
- 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 100mV/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 (<10eV) plasma in the magnetosphere with warm (similar to 100eV) 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.
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| 2. |
- Oieroset, M., et al.
(author)
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MMS observations of large guide field symmetric reconnection between colliding reconnection jets at the center of a magnetic flux rope at the magnetopause
- 2016
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In: Geophysical Research Letters. - : Blackwell Publishing. - 0094-8276 .- 1944-8007. ; 43:11, s. 5536-5544
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Journal article (peer-reviewed)abstract
- We report evidence for reconnection between colliding reconnection jets in a compressed current sheet at the center of a magnetic flux rope at Earth's magnetopause. The reconnection involved nearly symmetric inflow boundary conditions with a strong guide field of two. The thin (2.5 ion-skin depth (d(i)) width) current sheet (at similar to 12 d(i) downstream of the X line) was well resolved by MMS, which revealed large asymmetries in plasma and field structures in the exhaust. Ion perpendicular heating, electron parallel heating, and density compression occurred on one side of the exhaust, while ion parallel heating and density depression were shifted to the other side. The normal electric field and double out-of-plane (bifurcated) currents spanned almost the entire exhaust. These observations are in good agreement with a kinetic simulation for similar boundary conditions, demonstrating in new detail that the structure of large guide field symmetric reconnection is distinctly different from antiparallel reconnection.
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| 3. |
- Phan, T. D., et al.
(author)
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Electron magnetic reconnection without ion coupling in Earth's turbulent magnetosheath
- 2018
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In: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 557:7704, s. 202-
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Journal article (peer-reviewed)abstract
- Magnetic reconnection in current sheets is a magnetic-to-particle energy conversion process that is fundamental to many space and laboratory plasma systems. In the standard model of reconnection, this process occurs in a minuscule electron-scale diffusion region(1,2). On larger scales, ions couple to the newly reconnected magnetic-field lines and are ejected away from the diffusion region in the form of bi-directional ion jets at the ion Alfven speed(3-5). Much of the energy conversion occurs in spatially extended ion exhausts downstream of the diffusion region(6). In turbulent plasmas, which contain a large number of small-scale current sheets, reconnection has long been suggested to have a major role in the dissipation of turbulent energy at kinetic scales(7-11). However, evidence for reconnection plasma jetting in small-scale turbulent plasmas has so far been lacking. Here we report observations made in Earth's turbulent magnetosheath region (downstream of the bow shock) of an electron-scale current sheet in which diverging bi-directional super-ion-Alfvenic electron jets, parallel electric fields and enhanced magnetic-to-particle energy conversion were detected. Contrary to the standard model of reconnection, the thin reconnecting current sheet was not embedded in a wider ion-scale current layer and no ion jets were detected. Observations of this and other similar, but unidirectional, electron jet events without signatures of ion reconnection reveal a form of reconnection that can drive turbulent energy transfer and dissipation in electron-scale current sheets without ion coupling.
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| 4. |
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| 5. |
- Oieroset, M., et al.
(author)
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Spatial evolution of magnetic reconnection diffusion region structures with distance from the X-line
- 2021
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In: Physics of Plasmas. - : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 28:12
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Journal article (peer-reviewed)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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| 6. |
- Phan, T. D., et al.
(author)
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MMS observations of electron-scale filamentary currents in the reconnection exhaust and near the X line
- 2016
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In: Geophysical Research Letters. - : Blackwell Publishing. - 0094-8276 .- 1944-8007. ; 43:12, s. 6060-6069
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Journal article (peer-reviewed)abstract
- We report Magnetospheric Multiscale observations of macroscopic and electron-scale current layers in asymmetric reconnection. By intercomparing plasma, magnetic, and electric field data at multiple crossings of a reconnecting magnetopause on 22 October 2015, when the average interspacecraft separation was similar to 10 km, we demonstrate that the ion and electron moments are sufficiently accurate to provide reliable current density measurements at 30ms cadence. These measurements, which resolve current layers narrower than the interspacecraft separation, reveal electron-scale filamentary Hall currents and electron vorticity within the reconnection exhaust far downstream of the X line and even in the magnetosheath. Slightly downstream of the X line, intense (up to 3 mu A/m(2)) electron currents, a super-Alfvenic outflowing electron jet, and nongyrotropic crescent shape electron distributions were observed deep inside the ion-scale magnetopause current sheet and embedded in the ion diffusion region. These characteristics are similar to those attributed to the electron dissipation/diffusion region around the X line.
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| 7. |
- Eastwood, J. P., et al.
(author)
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Guide Field Reconnection : Exhaust Structure and Heating
- 2018
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In: Geophysical Research Letters. - : AMER GEOPHYSICAL UNION. - 0094-8276 .- 1944-8007. ; 45:10, s. 4569-4577
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Journal article (peer-reviewed)abstract
- Magnetospheric Multiscale observations are used to probe the structure and temperature profile of a guide field reconnection exhaust similar to 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 1 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 were 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.
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| 8. |
- Eastwood, J. P., et al.
(author)
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Ion-scale secondary flux ropes generated by magnetopause reconnection as resolved by MMS
- 2016
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In: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 43:10, s. 4716-4724
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Journal article (peer-reviewed)abstract
- New Magnetospheric Multiscale (MMS) observations of small-scale (similar to 7 ion inertial length radius) flux transfer events (FTEs) at the dayside magnetopause are reported. The 10 km MMS tetrahedron size enables their structure and properties to be calculated using a variety of multispacecraft techniques, allowing them to be identified as flux ropes, whose flux content is small (similar to 22 kWb). The current density, calculated using plasma and magnetic field measurements independently, is found to be filamentary. Intercomparison of the plasma moments with electric and magnetic field measurements reveals structured non-frozen-in ion behavior. The data are further compared with a particle-in-cell simulation. It is concluded that these small-scale flux ropes, which are not seen to be growing, represent a distinct class of FTE which is generated on the magnetopause by secondary reconnection.
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| 9. |
- Kacem, I., et al.
(author)
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Magnetic Reconnection at a Thin Current Sheet Separating Two Interlaced Flux Tubes at the Earth's Magnetopause
- 2018
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In: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 123:3, s. 1779-1793
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Journal article (peer-reviewed)abstract
- The occurrence of spatially and temporally variable reconnection at the Earth's magnetopause leads to the complex interaction of magnetic fields from the magnetosphere and magnetosheath. Flux transfer events (FTEs) constitute one such type of interaction. Their main characteristics are (1) an enhanced core magnetic field magnitude and (2) a bipolar magnetic field signature in the component normal to the magnetopause, reminiscent of a large-scale helicoidal flux tube magnetic configuration. However, other geometrical configurations which do not fit this classical picture have also been observed. Using high-resolution measurements from the Magnetospheric Multiscale mission, we investigate an event in the vicinity of the Earth's magnetopause on 7 November 2015. Despite signatures that, at first glance, appear consistent with a classic FTE, based on detailed geometrical and dynamical analyses as well as on topological signatures revealed by suprathermal electron properties, we demonstrate that this event is not consistent with a single, homogenous helicoidal structure. Our analysis rather suggests that it consists of the interaction of two separate sets of magnetic field lines with different connectivities. This complex three-dimensional interaction constructively conspires to produce signatures partially consistent with that of an FTE. We also show that, at the interface between the two sets of field lines, where the observed magnetic pileup occurs, a thin and strong current sheet forms with a large ion jet, which may be consistent with magnetic flux dissipation through magnetic reconnection in the interaction region.
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| 10. |
- Oieroset, M., et al.
(author)
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Reconnection With Magnetic Flux Pileup at the Interface of Converging ts at the Magnetopause
- 2019
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In: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 46:4, s. 1937-1946
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Journal article (peer-reviewed)abstract
- We report Magnetospheric Multiscale observations of reconnection in a in current sheet at the interface of interlinked flux tubes carried by nverging reconnection jets at Earth's magnetopause. The ion skin pth-scale width of the interface current sheet and the non-frozen-in ns indicate that Magnetospheric Multiscale crossed the reconnection yer near the X-line, through the ion diffusion region. Significant leup of the reconnecting component of the magnetic field in this and ree other events on approach to the interface current sheet was companied by an increase in magnetic shear and decrease in , leading conditions favorable for reconnection at the interface current sheet. e pileup also led to enhanced available magnetic energy per particle d strong electron heating. The observations shed light on the olution and energy release in 3-D systems with multiple reconnection tes. ain Language Summary The Earth and the solar wind magnetic fields terconnect through a process called magnetic reconnection. The newly connected magnetic field lines are strongly bent and accelerate rticles, similar to a rubber band in a slingshot. In this paper we ve used observations from NASA's Magnetospheric MultiScale spacecraft investigate what happens when two of these slingshot-like magnetic eld lines move toward each other and get tangled up. We found that the o bent magnetic field lines tend to orient themselves perpendicular to ch other as they become interlinked and stretched, similar to what bber bands would do. This reorientation allows the interlinked gnetic fields to reconnect again, releasing part of the built-up gnetic energy as strong electron heating. The results are important cause they show how interlinked magnetic fields, which occur in many lar and astrophysics contexts, reconnect and produce enhanced electron ating, something that was not understood before.
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