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- Title
Spacecraft Potential Changes Associated With EMIC Waves in the Inner Magnetosphere.
- Authors
Kim, Khan‐Hyuk; Lee, Junhyun; Kwon, Jong‐Woo; Lee, Ensang; Kim, Hee‐Eun; Jin, Ho; Kwon, Hyuck‐Jin; Baek, Seul‐Min; Wygant, John; Mozer, Forrest S.
- Abstract
Although electromagnetic ion cyclotron (EMIC) waves are commonly observed in the magnetosphere and are believed to energize background cold ions, it is not clear whether EMIC waves play a significant role in determining spacecraft potential change. In this paper, we present two strong He‐band EMIC wave events observed by the Van Allen Probe‐B spacecraft inside the plasmasphere. One event occurred on 11 March 2016 when the spacecraft was on the dayside, and the other occurred on 9 October 2016 when the spacecraft was in the postmidnight sector. When a strong He‐band EMIC wave activity was detected, low‐energy ion flux enhancements occurred nearly simultaneously with the EMIC wave power enhancements. Both events presented in this study are clearly unique in that He‐band wave power and enhanced proton flux are extremely high. During the wave activity interval, we found that the spacecraft charged more positively without a significant change in the ambient electron density. We discuss whether low‐energy ions energized by EMIC waves can contribute to the spacecraft potential change. Plain Language Summary: In the Earth's magnetosphere the spacecraft potential is determined by the current balance between escaping photoelectrons and incoming ambient electrons. Since the ions are considerably more massive than the electrons, implying that electrons are mobile than ions, the ion currents from the ambient plasma have been neglected for the current balance. Spacecraft interactions with the ambient plasma give rise to spacecraft charging. During the interval we focus on in this study, the spacecraft charged positively, indicating that the photoelectron current is larger than the electron current from the ambient plasma. When the spacecraft observed strong electromagnetic ion cyclotron (EMIC) wave activity, low‐energy proton, and helium ion flux enhancements occurred nearly simultaneously with the EMIC power enhancements. At the time of EMIC waves, the spacecraft charged more positively. From these observations, we suggest that wave‐associated low‐energy ion flux enhancements, corresponding to the accumulation of positive ions from the surrounding plasma on spacecraft surface, lead to more positive surface charging. Key Points: Low‐energy proton and helium ion flux enhancements occur nearly simultaneously with electromagnetic ion cyclotron (EMIC) wavesCold protons and helium ions below 1 eV are accelerated by EMIC wavesMore positive surface charging occurs during the interval of EMIC wave activity
- Subjects
MAGNETOSPHERE; HELIUM ions; PLASMA sheaths; OCEAN wave power; CATIONS; ELECTRON density; SPACE vehicles
- Publication
Journal of Geophysical Research. Space Physics, 2022, Vol 127, Issue 9, p1
- ISSN
2169-9380
- Publication type
Article
- DOI
10.1029/2022JA030337