University of Oulu

Thomas, N., Shiokawa, K., Miyoshi, Y., Kasahara, Y., Shinohara, I., Kumamoto, A., et al. (2021). Investigation of small‐scale electron density irregularities observed by the Arase and Van Allen Probes satellites inside and outside the plasmasphere. Journal of Geophysical Research: Space Physics, 126, e2020JA027917.

Investigation of small‐scale electron density irregularities observed by the Arase and Van Allen Probes satellites inside and outside the plasmasphere

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Author: Thomas, Neethal1,2; Shiokawa, Kazuo1; Miyoshi, Yoshizumi1;
Organizations: 1Institute for Space‐Earth Environmental Research, Nagoya University, Nagoya, Japan
2Sodankylä Geophysical Observatory, University of Oulu, Sodankylä, Finland
3Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Japan
4Institute of Space and Astronautical Science/Japan Aerospace Exploration Agency, Sagamihara, Japan
5Graduate School of Science, Tohoku University, Sendai, Japan
6Department of Earth and Planetary Science, The University of Tokyo, Tokyo, Japan
7Graduate School of Science, Osaka University, Osaka, Japan
8Academia Sinica Institute of Astronomy and Astrophysics, Taipei, Taiwan
9Institute of Space and Plasma Sciences, National Cheng Kung University, Tainan, Taiwan
10School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA
11NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
12Los Alamos National Laboratory, Los Alamos, New Mexico, USA
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 3.9 MB)
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Language: English
Published: American Geophysical Union, 2021
Publish Date: 2021-05-18


In situ electron density profiles obtained from Arase in the night magnetic local time (MLT) sector and from RBSP‐B covering all MLTs are used to study the small‐scale density irregularities present in the plasmasphere and near the plasmapause. Electron density perturbations with amplitudes >10% from background density and with time‐scales less than 30‐min are investigated here as the small‐scale density irregularities. The statistical survey of the density irregularities is carried out using nearly 2 years of density data obtained from RBSP‐B and 4 months of data from Arase satellites. The results show that density irregularities are present globally at all MLT sectors and L‐shells both inside and outside the plasmapause, with a higher occurrence at L > 4. The occurrence of density irregularities is found to be higher during disturbed geomagnetic and interplanetary conditions. The case studies presented here revealed: (1) The plasmaspheric density irregularities observed during both quiet and disturbed conditions are found to coexist with the hot plasma sheet population. (2) During quiet periods, the plasma waves in the whistler‐mode frequency range are found to be modulated by the small‐scale density irregularities, with density depletions coinciding well with the decrease in whistler intensity. Our observations suggest that different source mechanisms are responsible for the generation of density structures at different MLTs and geomagnetic conditions.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 126
Issue: 3
Pages: 1 - 18
DOI: 10.1029/2020JA027917
Type of Publication: A1 Journal article – refereed
Field of Science: 114 Physical sciences
1171 Geosciences
115 Astronomy and space science
Copyright information: © 2021. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.