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Title: Statistical analysis of MMS observations of energetic electron escape observed at/beyond the dayside magnetopause

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 observations 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 ismore » 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
Authors:
ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [3] ; ORCiD logo [3] ; ORCiD logo [3] ; ORCiD logo [4] ; ORCiD logo [4] ; ORCiD logo [4] ; ORCiD logo [5] ; ORCiD logo [6] ; ORCiD logo [2] ; ORCiD logo [7] ; ORCiD logo [8] ; ORCiD logo [9]
  1. The Johns Hopkins Univ. Applied Physics Lab., Laurel, MD (United States)
  2. NASA Goddard Space Flight Center, Greenbelt, MD (United States)
  3. The Aerospace Corporation, El Segundo, CA (United States)
  4. Lab. for Atmospheric and Space Physics, Boulder, CO (United States)
  5. Univ. of New Hampshire, Durham, NH (United States)
  6. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  7. Univ. of California, Los Angeles, CA (United States)
  8. Univ. of New Hampshire, Durham, NH (United States); Southwest Research Institute, San Antonio, TX (United States)
  9. Southwest Research Institute, San Antonio, TX (United States); Univ. of Texas at San Antonio, San Antonio, TX (United States)
Publication Date:
Report Number(s):
LA-UR-17-28034
Journal ID: ISSN 2169-9380; TRN: US1703020
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Space Physics
Additional Journal Information:
Journal Volume: 122; Journal Issue: 9; Journal ID: ISSN 2169-9380
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:
1402653