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Title: Energy limits of electron acceleration in the plasma sheet during substorms: A case study with the Magnetospheric Multiscale (MMS) mission

Here, we present multipoint observations of earthward moving dipolarization fronts and energetic particle injections from NASA's Magnetospheric Multiscale mission with a focus on electron acceleration. From a case study during a substorm on 02 August 2015, we find that electrons are only accelerated over a finite energy range, from a lower energy threshold at ~7–9 keV up to an upper energy cutoff in the hundreds of keV range. At energies lower than the threshold energy, electron fluxes decrease, potentially due to precipitation by strong parallel electrostatic wavefields or initial sources in the lobes. Electrons at energies higher than the threshold are accelerated cumulatively by a series of impulsive magnetic dipolarization events. This case demonstrates how the upper energy cutoff increases, in this case from ~130 keV to >500 keV, with each dipolarization/injection during sustained activity. We also present a simple model accounting for these energy limits that reveals that electron energization is dominated by betatron acceleration.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [3] ;  [3] ;  [3] ;  [3] ; ORCiD logo [4] ;  [5] ;  [5] ;  [5] ;  [5] ;  [6] ;  [7] ;  [7] ;  [8] ;  [8] more »;  [8] ;  [8] ;  [8] ;  [9] ;  [9] ;  [10] « less
  1. The Aerospace Corp., El Segundo, CA (United States)
  2. Johns Hopkins Univ., Laurel, MD (United States)
  3. Univ. of Colorado, Boulder, CO (United States)
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  5. NASA Goddard Space Flight Center, Greenbelt, MD (United States)
  6. NASA Goddard Space Flight Center, Greenbelt, MD (United States); Denali Scientific, Healy, AK (United States)
  7. Austrian Academy of Sciences, Graz (Austria)
  8. Univ. of California, Los Angeles, CA (United States)
  9. Univ. of New Hampshire, Durham, NH (United States)
  10. Southwest Research Institute, San Antonio, TX (United States)
Publication Date:
Report Number(s):
LA-UR-16-23139
Journal ID: ISSN 0094-8276
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 43; Journal Issue: 15; Journal ID: ISSN 0094-8276
Publisher:
American Geophysical Union
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
National Aeronautic and Space Administration (NASA); USDOE
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; heliospheric and magnetospheric physics
OSTI Identifier:
1340970