Journal article
The Characteristics of EMIC Waves in the Magnetosphere Based on the Van Allen Probes and Arase Observations
Journal of geophysical research. Space physics, Vol.126(6), e2020JA029001
06/2021
DOI: 10.1029/2020JA029001
Abstract
We performed a comprehensive statistical study of electromagnetic ion cyclotron (EMIC) waves observed by the Van Allen Probes and Exploration of energization and Radiation in Geospace satellite (ERG/Arase). From 2017 to 2018, we identified and categorized EMIC wave events with respect to wavebands (H+ and He+ EMIC waves) and relative locations from the plasmasphere (inside and outside the plasmasphere). We found that H+ EMIC waves in the morning sector at L > 8 are predominantly observed with a mixture of linear and right‐handed polarity and higher wave normal angles during quiet geomagnetic conditions. Both H+ and He+ EMIC waves observed in the noon sector at L ∼ 4–6 have left‐handed polarity and lower wave normal angles at |MLAT| < 20° during the recovery phase of a storm with moderate solar wind pressure. In the afternoon sector (12–18 MLT), He+ EMIC waves are dominantly observed with strongly enhanced wave power at L ∼ 6–8 during the storm main phase, while in the dusk sector (17–21 MLT) they have lower wave normal angles with linear polarity at L > 8 during geomagnetic quiet conditions. Based on distinct characteristics at different EMIC wave occurrence regions, we suggest that EMIC waves in the magnetosphere can be generated by different free energy sources. Possible sources include the freshly injected particles from the plasma sheet, adiabatic heating by dayside magnetospheric compressions, suprathermal proton heating by magnetosonic waves, and off‐equatorial sources.
Key Points
Electromagnetic ion cyclotron (EMIC) waves in the magnetosphere have four major occurrence regions excited by possibly different generation processes
For He‐EMIC waves in the afternoon sector, injected particles and off‐equatorial sources are the major driver at L ∼ 6 and L > 8, respectively
H‐EMIC waves are generated by enhancing dynamic pressure in the noon sector at L < 6, or suprathermal protons in the dawn sector at L > 8
Details
- Title: Subtitle
- The Characteristics of EMIC Waves in the Magnetosphere Based on the Van Allen Probes and Arase Observations
- Creators
- Chae‐Woo Jun - Nagoya UniversityYoshizumi Miyoshi - Nagoya UniversitySatoshi Kurita - Kyoto UniversityChao Yue - Peking UniversityJacob Bortnik - University of California, Los AngelesLarry Lyons - University of CaliforniaSatoko Nakamura - Nagoya UniversityMasafumi Shoji - Nagoya UniversityShun Imajo - Nagoya UniversityCraig Kletzing - Department of Physics and Astronomy University of Lowa Lowa USAYoshiya Kasahara - Kanazawa UniversityYasumasa Kasaba - Tohoku UniversityShoya Matsuda - Japan Aerospace Exploration AgencyFuminori Tsuchiya - Tohoku UniversityAtsushi Kumamoto - Tohoku UniversityAyako Matsuoka - Kyoto UniversityIku Shinohara - Japan Aerospace Exploration Agency
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Space physics, Vol.126(6), e2020JA029001
- DOI
- 10.1029/2020JA029001
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Number of pages
- 21
- Grant note
- JSPS KAKENHI (15H05815; 15H05747; 16H06286; 17H00728; 20H01959) National Key R&D Program of China (2020YFE0202100) Japan Society for the Promotion of Science National Natural Science Foundation of China (NSFC) (41974191) China National Space Administration Project (D020303)
- Language
- English
- Date published
- 06/2021
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984428803802771
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