Title: Ultrarelativistic electron butterfly distributions created by parallel acceleration due to magnetosonic waves

Abstract

The Van Allen Probe observations during the recovery phase of a large storm that occurred on 17 March 2015 showed that the ultrarelativistic electrons at the inner boundary of the outer radiation belt (L* = 2.6–3.7) exhibited butterfly pitch angle distributions, while the inner belt and the slot region also showed evidence of sub-MeV electron butterfly distributions. In this paper, strong magnetosonic waves were observed in the same regions and at the same time periods as these butterfly distributions. Moreover, when these magnetosonic waves extended to higher altitudes (L* = 4.1), the butterfly distributions also extended to the same region. Combining test particle calculations and Fokker-Planck diffusion simulations, we successfully reproduced the formation of the ultrarelativistic electron butterfly distributions, which primarily result from parallel acceleration caused by Landau resonance with magnetosonic waves. Finally, the coexistence of ultrarelativistic electron butterfly distributions with magnetosonic waves was also observed in the 24 June 2015 storm, providing further support that the magnetosonic waves play a key role in forming butterfly distributions.

Authors:

Li, Jinxing ^[1]; Bortnik, Jacob ^[1]; Thorne, Richard M. ^[1]; Li, Wen ^[1]; Ma, Qianli  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-5452-4756"

Baker, Daniel N. ^[2]; Reeves, Geoffrey D.  ^[3];

• Search DOE PAGES for author "Reeves, Geoffrey D."
• Search DOE PAGES for ORCID "0000-0002-7985-8098"

Fennell, Joseph F. ^[4]; Spence, Harlan E. ^[5]; Kletzing, Craig A. ^[6]; Kurth, William S. ^[6]; Hospodarsky, George B. ^[6]; Angelopoulos, Vassilis ^[7]; Blake, J. Bernard. ^[4]

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+ Show Author Affiliations

1. Univ. of California, Los Angeles, CA (United States). Dept. of Atmospheric and Oceanic Sciences
2. Univ. of Colorado, Boulder, CO (United States). Lab. for Atmospheric and Space Physics
3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
4. The Aerospace Corporation, El Segundo, CA (United States). Space Science Applications Lab.
5. Univ. of New Hampshire, Durham, NH (United States). Inst. for the Study of Earth, Oceans, and Space
6. Univ. of Iowa, Iowa City, IA (United States). Dept. of Physics and Astronomy
7. Univ. of California, Los Angeles, CA (United States). Dept. of Earth, Planetary, and Space Sciences. Inst. of Geophysics and Planetary Physics

Publication Date:

Wed Apr 13 00:00:00 EDT 2016

Research Org.:

Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Univ. of California, Los Angeles, CA (United States); The Aerospace Corporation, El Segundo, CA (United States); Univ. of Iowa, Iowa City, IA (United States)

Sponsoring Org.:

USDOE; National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); US Air Force Office of Scientific Research (AFOSR)

OSTI Identifier:

1467365

Report Number(s):

LA-UR-16-23142
Journal ID: ISSN 2169-9380

Grant/Contract Number:  

AC52-06NA25396; NAS5-01072; NNX13AI61G; NNX11AR64G; NNX15AF61G; NNX15AI96G; 921647; 967399; AGS-1103064; 1001057397:01; 13-041; FA9550-15-1-0158

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Geophysical Research. Space Physics

Additional Journal Information:

Journal Volume: 121; Journal Issue: 4; Journal ID: ISSN 2169-9380

Publisher:

American Geophysical Union

Country of Publication:

United States

Language:

English

Subject:

79 ASTRONOMY AND ASTROPHYSICS; butterfly distributions; magnetosonic waves; radiation belt; Landau resonance; ultrarelativistic electrons