Investigation of Small-Scale Electron Density Irregularities Observed by the Arase and Van Allen Probes Satellites Inside and Outside the Plasmasphere

Journal Article · Thu Mar 18 00:00:00 EDT 2021 · Journal of Geophysical Research. Space Physics

DOI:https://doi.org/10.1029/2020ja027917· OSTI ID:1804358

Thomas, Neethal ^[1]; Shiokawa, Kazuo ^[2]; Miyoshi, Yoshizumi ^[2]; Kasahara, Yoshiya ^[3]; Shinohara, Iku ^[4]; Kumamoto, Atsushi ^[5]; Tsuchiya, Fuminori ^[5]; Matsuoka, Ayako ^[4]; Kasahara, Satoshi ^[6]; Yokota, Shoichiro ^[7]; Keika, Kunihiro ^[6]; Hori, Tomoaki ^[2]; Asamura, Kazushi ^[4]; Wang, Shiang‐Yu ^[8]; Kazama, Yoichi ^[8]; Tam, Sunny Wing‐Yee ^[9]; Chang, Tzu‐Fang ^[10]; Wang, Bo‐Jhou ^[8]; Wygant, John ^[11]; Breneman, Aaron ^[12] ; Reeves, Geoffrey ^[13]

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1. Nagoya Univ. (Japan); Univ. of Oulu, Sodankylä (Finland)
2. Nagoya Univ. (Japan)
3. Kanazawa Univ. (Japan)
4. Japan Aerospace Exploration Agency (ISAS/JAXA), Sagamihara, Kanagawa (Japan)
5. Tohoku Univ., Sendai (Japan)
6. Univ. of Tokyo (Japan)
7. Osaka Univ. (Japan)
8. Academia Sinica, Taipei (Taiwan)
9. National Cheng Kung Univ., Tainan City (Taiwan)
10. Nagoya Univ. (Japan); National Cheng Kung Univ., Tainan City (Taiwan)
11. Univ. of Minnesota, Minneapolis, MN (United States)
12. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
13. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

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.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: Japan Society for the Promotion of Science (JSPS); National Aeronautics and Space Administration (NASA); USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: 89233218CNA000001
• OSTI ID: 1804358
• Report Number(s): LA-UR--20-28813
• Journal Information: Journal of Geophysical Research. Space Physics, Journal Name: Journal of Geophysical Research. Space Physics Journal Issue: 3 Vol. 126; ISSN 2169-9380
• Publisher: American Geophysical Union
• Country of Publication: United States
• Language: English

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