TY - JOUR
T1 - Relative Contribution of ULF Waves and Whistler-Mode Chorus to the Radiation Belt Variation During the May 2017 Storm
AU - Takahashi, Naoko
AU - Seki, Kanako
AU - Fok, Mei Ching
AU - Zheng, Yihua
AU - Miyoshi, Yoshizumi
AU - Kasahara, Satoshi
AU - Keika, Kunihiro
AU - Hartley, David
AU - Kasahara, Yoshiya
AU - Kasaba, Yasumasa
AU - Higashio, Nana
AU - Matsuoka, Ayako
AU - Yokota, Shoichiro
AU - Hori, Tomoaki
AU - Shoji, Masafumi
AU - Nakamura, Satoko
AU - Imajo, Shun
AU - Shinohara, Iku
N1 - Funding Information:
This work was supported by the Ministry of Education, Culture, Sports, Science and Technology, Japan Society for the Promotion of Science 16H06286, 18KK0099, 15H05815, 20H01957, and 20H01959.
Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.
PY - 2021/11
Y1 - 2021/11
N2 - We investigate the time and location where ULF waves and whistler-mode chorus contributed to the net flux enhancement of relativistic electrons during the magnetic storm of May 2017. During the early recovery phase, both ULF and chorus waves contribute to the enhancement of relativistic electron fluxes, but ULF waves play roles of the inward diffusion. During the late recovery phase, both Van Allen Probe-B and Arase show that whistler-mode chorus contributes to the flux enhancement confined in the L-value. The CRCM coupled with BATS-R-US simulation qualitatively reproduces the global evolution of ULF waves. Although the electron flux is underestimated by the simulation, this study reveals a large anisotropy of hot electrons in the region where whistler-mode chorus waves were actually observed by satellites. In addition, the estimated magnetic field curvature on the dayside is small during the recovery phase. Furthermore, we investigate the control of wave evolution. Both observations and the simulation suggest that the observed ULF waves in the frequency range of ∼2–5 mHz are excited by the enhancement of the solar wind dynamic pressure. Observations also indicate that whistler-mode chorus on the nightside is predominantly excited by hot electrons with temperature anisotropy, whereas the dayside chorus is enhanced by the change of the magnetic field line configuration. The estimated spatial distributions of electron anisotropy and magnetic field curvature provide an explanation for the presence of enhanced whistler-mode chorus in the dusk sector, which is far from the usual location of wave generation.
AB - We investigate the time and location where ULF waves and whistler-mode chorus contributed to the net flux enhancement of relativistic electrons during the magnetic storm of May 2017. During the early recovery phase, both ULF and chorus waves contribute to the enhancement of relativistic electron fluxes, but ULF waves play roles of the inward diffusion. During the late recovery phase, both Van Allen Probe-B and Arase show that whistler-mode chorus contributes to the flux enhancement confined in the L-value. The CRCM coupled with BATS-R-US simulation qualitatively reproduces the global evolution of ULF waves. Although the electron flux is underestimated by the simulation, this study reveals a large anisotropy of hot electrons in the region where whistler-mode chorus waves were actually observed by satellites. In addition, the estimated magnetic field curvature on the dayside is small during the recovery phase. Furthermore, we investigate the control of wave evolution. Both observations and the simulation suggest that the observed ULF waves in the frequency range of ∼2–5 mHz are excited by the enhancement of the solar wind dynamic pressure. Observations also indicate that whistler-mode chorus on the nightside is predominantly excited by hot electrons with temperature anisotropy, whereas the dayside chorus is enhanced by the change of the magnetic field line configuration. The estimated spatial distributions of electron anisotropy and magnetic field curvature provide an explanation for the presence of enhanced whistler-mode chorus in the dusk sector, which is far from the usual location of wave generation.
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U2 - 10.1029/2020JA028972
DO - 10.1029/2020JA028972
M3 - Article
AN - SCOPUS:85119677488
VL - 126
JO - Journal of Geophysical Research: Space Physics
JF - Journal of Geophysical Research: Space Physics
SN - 2169-9380
IS - 11
M1 - e2020JA028972
ER -