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Title: A positive correlation between energetic electron butterfly distributions and magnetosonic waves in the radiation belt slot region

Energetic (hundreds of keV) electrons in the radiation belt slot region have been found to exhibit the butterfly pitch angle distributions. Resonant interactions with magnetosonic and whistler-mode waves are two potential mechanisms for the formation of these peculiar distributions. Here we perform a statistical study of energetic electron pitch angle distribution characteristics measured by Van Allen Probes in the slot region during a three-year period from May 2013 to May 2016. Our results show that electron butterfly distributions are closely related to magnetosonic waves rather than to whistlermode waves. Both electron butterfly distributions and magnetosonic waves occur more frequently at the geomagnetically active times than at the quiet times. In a statistical sense, more distinct butterfly distributions usually correspond to magnetosonic waves with larger amplitudes and vice versa. The averaged magnetosonic wave amplitude is less than 5 pT in the case of normal and flat-top distributions with a butterfly index BI = 1 but reaches ~ 35–95 pT in the case of distinct butterfly distributions with BI > 1:3. For magnetosonic waves with amplitudes > 50 pT, the occurrence rate of butterfly distribution is above 80%. Our study suggests that energetic electron butterfly distributions in the slot region are primarilymore » caused by magnetosonic waves.« less
Authors:
 [1] ;  [2] ;  [3] ;  [2] ;  [2] ;  [2] ; ORCiD logo [4] ;  [5] ;  [6] ;  [7] ; ORCiD logo [4]
  1. Changsha Univ. of Science and Technology (China); Univ. of Science and Technology of China, Hefei (China)
  2. Univ. of Science and Technology of China, Hefei (China)
  3. Changsha Univ. of Science and Technology (China)
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  5. Univ. of New Hampshire, Durham, NH (United States)
  6. Univ. of Colorado, Boulder, CO (United States)
  7. Aerospace Corp., Los Angeles, CA (United States)
Publication Date:
Report Number(s):
LA-UR-17-24833
Journal ID: ISSN 0094-8276; TRN: US1702887
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 44; Journal Issue: 9; 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:
79 ASTRONOMY AND ASTROPHYSICS; Heliospheric and Magnetospheric Physics
OSTI Identifier:
1402641