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Title: Energetic electron acceleration observed by MMS in the vicinity of an X-line crossing

Abstract

During the first months of observations, the Magnetospheric Multiscale Fly's Eye Energetic Particle Spectrometer instrument has observed several instances of electron acceleration up to >100 keV while in the vicinity of the dayside reconnection region. While particle acceleration associated with magnetic reconnection has been seen to occur up to these energies in the tail region, it had not yet been reported at the magnetopause. This study reports on observations of electron acceleration up to hundreds of keV that were recorded on 19 September 2015 around 1000 UT, in the midst of an X-line crossing. In the region surrounding the X-line, whistler-mode and broadband electrostatic waves were observed simultaneously with the appearance of highly energetic electrons which exhibited significant energization in the perpendicular direction. The mechanisms by which particles may be accelerated via reconnection-related processes are intrinsic to understanding particle dynamics among a wide range of spatial scales and plasma environments.

Authors:
 [1];  [2];  [1];  [3];  [1];  [2];  [2];  [4];  [4]; ORCiD logo [5];  [1];  [6];  [6];  [7];  [8]
  1. Univ. of Colorado, Boulder, CO (United States)
  2. The Aerospace Corporation, El Segundo, CA (United States)
  3. Aalto Univ., Otaniemi (Finland)
  4. The Johns Hopkins University Applied Physics Lab., Laurel, MD (United States)
  5. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  6. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
  7. Univ. of New Hampshire, Durham, NH (United States)
  8. Southwest Research Inst. (SwRI), San Antonio, TX (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
National Aeronautic and Space Administration (NASA); USDOE
OSTI Identifier:
1402635
Report Number(s):
LA-UR-17-24824
Journal ID: ISSN 0094-8276; TRN: US1702885
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 43; Journal Issue: 14; Journal ID: ISSN 0094-8276
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; Heliospheric and Magnetospheric Physics

Citation Formats

Jaynes, A. N., Turner, D. L., Wilder, F. D., Osmane, A., Baker, D. N., Blake, J. B., Fennell, J. F., Cohen, I. J., Mauk, B. H., Reeves, G. D., Ergun, R. E., Giles, B. L., Gershman, D. J., Torbert, R. B., and Burch, J. L. Energetic electron acceleration observed by MMS in the vicinity of an X-line crossing. United States: N. p., 2016. Web. doi:10.1002/2016GL069206.
Jaynes, A. N., Turner, D. L., Wilder, F. D., Osmane, A., Baker, D. N., Blake, J. B., Fennell, J. F., Cohen, I. J., Mauk, B. H., Reeves, G. D., Ergun, R. E., Giles, B. L., Gershman, D. J., Torbert, R. B., & Burch, J. L. Energetic electron acceleration observed by MMS in the vicinity of an X-line crossing. United States. doi:10.1002/2016GL069206.
Jaynes, A. N., Turner, D. L., Wilder, F. D., Osmane, A., Baker, D. N., Blake, J. B., Fennell, J. F., Cohen, I. J., Mauk, B. H., Reeves, G. D., Ergun, R. E., Giles, B. L., Gershman, D. J., Torbert, R. B., and Burch, J. L. Mon . "Energetic electron acceleration observed by MMS in the vicinity of an X-line crossing". United States. doi:10.1002/2016GL069206. https://www.osti.gov/servlets/purl/1402635.
@article{osti_1402635,
title = {Energetic electron acceleration observed by MMS in the vicinity of an X-line crossing},
author = {Jaynes, A. N. and Turner, D. L. and Wilder, F. D. and Osmane, A. and Baker, D. N. and Blake, J. B. and Fennell, J. F. and Cohen, I. J. and Mauk, B. H. and Reeves, G. D. and Ergun, R. E. and Giles, B. L. and Gershman, D. J. and Torbert, R. B. and Burch, J. L.},
abstractNote = {During the first months of observations, the Magnetospheric Multiscale Fly's Eye Energetic Particle Spectrometer instrument has observed several instances of electron acceleration up to >100 keV while in the vicinity of the dayside reconnection region. While particle acceleration associated with magnetic reconnection has been seen to occur up to these energies in the tail region, it had not yet been reported at the magnetopause. This study reports on observations of electron acceleration up to hundreds of keV that were recorded on 19 September 2015 around 1000 UT, in the midst of an X-line crossing. In the region surrounding the X-line, whistler-mode and broadband electrostatic waves were observed simultaneously with the appearance of highly energetic electrons which exhibited significant energization in the perpendicular direction. The mechanisms by which particles may be accelerated via reconnection-related processes are intrinsic to understanding particle dynamics among a wide range of spatial scales and plasma environments.},
doi = {10.1002/2016GL069206},
journal = {Geophysical Research Letters},
number = 14,
volume = 43,
place = {United States},
year = {Mon Jul 25 00:00:00 EDT 2016},
month = {Mon Jul 25 00:00:00 EDT 2016}
}

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  • Here, observations from the Energetic Particle Detector (EPD) instrument suite aboard the Magnetospheric Multiscale (MMS) spacecraft show that energetic (greater than tens of keV) magnetospheric particle escape into the magnetosheath occurs commonly across the dayside. This includes the surprisingly frequent observation of magnetospheric electrons in the duskside magnetosheath, an unexpected result given assumptions regarding magnetic drift shadowing. The 238 events identified in the 40 keV electron energy channel during the first MMS dayside season that exhibit strongly anisotropic pitch angle distributions indicating monohemispheric field-aligned streaming away from the magnetopause. A review of the extremely rich literature of energetic electron observationsmore » beyond the magnetopause is provided to place these new observations into historical context. Despite the extensive history of such research, these new observations provide a more comprehensive data set that includes unprecedented magnetic local time (MLT) coverage of the dayside equatorial magnetopause/magnetosheath. These data clearly highlight the common escape of energetic electrons along magnetic field lines concluded to have been reconnected across the magnetopause. While these streaming escape events agree with prior studies which show strong correlation with geomagnetic activity (suggesting a magnetotail source) and occur most frequently during periods of southward IMF, the high number of duskside events is unexpected and previously unobserved. Although the lowest electron energy channel was the focus of this study, the events reported here exhibit pitch angle anisotropies indicative of streaming up to 200 keV, which could represent the magnetopause loss of >1 MeV electrons from the outer radiation belt.« less
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  • We have analyzed energetic protons in the energy range 30 to 500 keV and energetic electrons > or =75 keV obtained with the Max-Planck-Institut/University of Maryland sensor system on ISEE-1 during a plasma sheet crossing on March 26, 1978. The behavior of protons with energies of more than approx.100 keV is very different from that of the approx.30 to approx.100 keV protons which represent the suprathermal tail of the plasma sheet distribution. The more energetic ions appear on a time scale of serveral minutes following a northward turning of the tail magnetic field. At about the same time the plassmamore » measurements show a velocity of approx.200 km/s in the tailward direction. This velocity enhancement is first seen at ISEE-1 and later on at ISEE-2, which is earthward of ISEE-1. The temporal sequence of the energetic particle, magnetic field, and plasma observations and the proton and electron anisotropies are discussed in terms of acceleration near a magnetic neutral line which occurs well within the plasma sheet. In this framework the magnetic neutral line would move earthward, followed by a magnetic island. The extent of the neutral line would be limited to the dusk side of the tail. No disruption of the plasma sheet is observed as compared to large-scale substorm activity.« less
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