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Title: Rapid enhancement of low energy (<100 eV) ion flux in response to interplanetary shocks based on two Van Allen Probes case studies: Implications for source regions and heating mechanisms

Interactions between interplanetary (IP) shocks and the Earth's magnetosphere manifest many important space physics phenomena including low-energy ion flux enhancements and particle acceleration. In order to investigate the mechanisms driving shock-induced enhancement of low-energy ion flux, we have examined two IP shock events that occurred when the Van Allen Probes were located near the equator while ionospheric and ground observations were available around the spacecraft footprints. We have found that, associated with the shock arrival, electromagnetic fields intensified, and low-energy ion fluxes, including H+, He+, and O+, were enhanced dramatically in both the parallel and perpendicular directions. During the 2 October 2013 shock event, both parallel and perpendicular flux enhancements lasted more than 20 min with larger fluxes observed in the perpendicular direction. In contrast, for the 15 March 2013 shock event, the low-energy perpendicular ion fluxes increased only in the first 5 min during an impulse of electric field, while the parallel flux enhancement lasted more than 30 min. In addition, ionospheric outflows were observed after shock arrivals. From a simple particle motion calculation, we found that the rapid response of low-energy ions is due to drifts of plasmaspheric population by the enhanced electric field. Furthermore, the fast accelerationmore » in the perpendicular direction cannot solely be explained by E × B drift but betatron acceleration also plays a role. Adiabatic acceleration may also explain the fast response of the enhanced parallel ion fluxes, while ion outflows may contribute to the enhanced parallel fluxes that last longer than the perpendicular fluxes.« less
Authors:
 [1] ;  [2] ;  [3] ;  [2] ;  [4] ;  [2] ;  [2] ;  [2] ;  [5] ;  [6] ;  [7] ;  [8]
  1. UCLA, Los Angeles, CA (United States); Univ. Corp. for Atmospheric Research, Boulder, CO (United States)
  2. UCLA, Los Angeles, CA (United States)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); New Mexico Consortium, Los Alamos, NM (United States)
  4. Peking Univ., Beijing (China)
  5. Univ. of New Hampshire, Durham, NH (United States)
  6. Univ. of Iowa, Iowa City, IA (United States)
  7. Univ. of Minnesota, Minneapolis, MN (United States)
  8. SRI International, Menlo Park, CA (United States)
Publication Date:
OSTI Identifier:
1291234
Report Number(s):
LA-UR--16-23136
Journal ID: ISSN 2169-9380
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Space Physics
Additional Journal Information:
Journal Name: Journal of Geophysical Research. Space Physics; Journal ID: ISSN 2169-9380
Publisher:
American Geophysical Union
Research Org:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Org:
NASA; USDOE
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES heliospheric and magnetospheric physics