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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

Abstract

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,more » the fast acceleration 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:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
National Aeronautic and Space Administration (NASA); USDOE
OSTI Identifier:
1291234
Report Number(s):
LA-UR-16-23136
Journal ID: ISSN 2169-9380
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: 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
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Heliospheric and Magnetospheric Physics

Citation Formats

Yue, Chao, Li, Wen, Reeves, Geoffrey D., Nishimura, Yukitoshi, Zong, Qiugang, Ma, Qianli, Bortnik, Jacob, Thorne, Richard M., Spence, Harlan E., Kletzing, Craig A., Wygant, John R., and Nicolls, Michael J.. 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. United States: N. p., 2016. Web. doi:10.1002/2016JA022808.
Yue, Chao, Li, Wen, Reeves, Geoffrey D., Nishimura, Yukitoshi, Zong, Qiugang, Ma, Qianli, Bortnik, Jacob, Thorne, Richard M., Spence, Harlan E., Kletzing, Craig A., Wygant, John R., & Nicolls, Michael J.. 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. United States. doi:10.1002/2016JA022808.
Yue, Chao, Li, Wen, Reeves, Geoffrey D., Nishimura, Yukitoshi, Zong, Qiugang, Ma, Qianli, Bortnik, Jacob, Thorne, Richard M., Spence, Harlan E., Kletzing, Craig A., Wygant, John R., and Nicolls, Michael J.. Fri . "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". United States. doi:10.1002/2016JA022808. https://www.osti.gov/servlets/purl/1291234.
@article{osti_1291234,
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},
author = {Yue, Chao and Li, Wen and Reeves, Geoffrey D. and Nishimura, Yukitoshi and Zong, Qiugang and Ma, Qianli and Bortnik, Jacob and Thorne, Richard M. and Spence, Harlan E. and Kletzing, Craig A. and Wygant, John R. and Nicolls, Michael J.},
abstractNote = {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 acceleration 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.},
doi = {10.1002/2016JA022808},
journal = {Journal of Geophysical Research. Space Physics},
number = ,
volume = ,
place = {United States},
year = {Fri Jul 01 00:00:00 EDT 2016},
month = {Fri Jul 01 00:00:00 EDT 2016}
}

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  • Here, we report observational evidence of cold plamsmaspheric electron (< 200 eV) acceleration by ultra-low-frequency (ULF) waves in the plasmaspheric boundary layer on 10 September 2015. Strongly enhanced cold electron fluxes in the energy spectrogram were observed along with second harmonic mode waves with a period of about 1 minute which lasted several hours during two consecutive Van Allen Probe B orbits. Cold electron (<200 eV) and energetic proton (10-20 keV) bi-directional pitch angle signatures observed during the event are suggestive of the drift-bounce resonance mechanism. The correlation between enhanced energy fluxes and ULF waves leads to the conclusions thatmore » plasmaspheric dynamics is strongly affected by ULF waves. Van Allen Probe A and B, GOES 13, GOES 15 and MMS 1 observations suggest ULF waves in the event were strongest on the dusk-side magnetosphere. Measurements from MMS 1 contain no evidence of an external wave source during the period when ULF waves and injected energetic protons with a bump-on-tail distribution were detected by Van Allen Probe B. This suggests that the observed ULF waves were probably excited by a localized drift-bounce resonant instability, with the free energy supplied by substorm-injected energetic protons. The observations by Van Allen Probe B suggest that energy transfer between particle species in different energy ranges can take place through the action of ULF waves, demonstrating the important role of these waves in the dynamical processes of the inner magnetosphere.« less
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