Relative Contribution of ULF Waves and Whistler‐Mode Chorus to the Radiation Belt Variation During the May 2017 Storm

Takahashi, Naoko; Seki, K.; Fok, M. C. H.; Zheng, Yihua; Miyoshi, Yoshizumi; Kasahara, Satoshi; Keika, K.; Hartley, D. P.; Kasahara, Yoshiya; Kasaba, Yasumasa; Higashio, Nana; Matsuoka, A.; Yokota, Shoichiro; Hori, Tomoaki; Motomizu, Shoji; Nakamura, Satoko; Imajo, Shun; Shinohara, I.

doi:10.1029/2020ja028972

Cited by 2 publications

(2 citation statements)

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“…For this geomagnetic storm during the initial phase of electron acceleration the solar wind speed is not high (~ 400 km/s), the relativistic electron fluxes reach a high level at lower L-shells. The solar wind density increase can also generate ULF waves in magnetosphere (Takahashi et al 2021) due to FLR or cavity/waveguide mode. Therefore, we suggest that a high solar wind velocity is not always a necessary factor for the relativistic electron growth.…”

Section: May-june 2017mentioning

confidence: 99%

“…Chorus emissions have some very particular property that makes them effective: they occur outside the plasmapause in a fairly narrow frequency band and propagate away from the magnetic equator where they are generated. Their source is the instability of electrons with energy ~ tens of keV injected during substorms, so the chorus emission intensity closely correlates with the substorm activity (Meredith et al 2002;Jaynes et al 2015;Takahashi et al 2021). The excited chorus emission supposedly accelerates locally electrons with ~ hundreds of keV to MeV energies.…”

Section: Introductionmentioning

confidence: 99%

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Relativistic electron flux growth during storm and non-storm periods as observed by ARASE and GOES satellites

Belakhovsky,

Pilipenko,

Antonova

et al. 2023

Earth Planets Space

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Variations of relativistic electron fluxes (E ≥ 1 MeV) and wave activity in the Earth magnetosphere are studied to determine the contribution of different acceleration mechanisms of the outer radiation belt electrons: ULF mechanism, VLF mechanism, and adiabatic acceleration. The electron fluxes were measured by Arase satellite and geostationary GOES satellites. The ULF power index is used to characterize the magnetospheric wave activity in the Pc5 range. To characterize the VLF wave activity in the magnetosphere, we use data from PWE instrument of Arase satellite. We consider some of the most powerful magnetic storms during the Arase era: May 27–29, 2017; September 7–10, 2017; and August 25–28, 2018. Also, non-storm intervals with a high solar wind speed before and after these storms for comparison are analyzed. Magnitudes of relativistic electron fluxes during these magnetic storms are found to be greater than that during non-storm intervals with high solar wind streams. During magnetic storms, the flux intensity maximum shifts to lower L-shells compared to intervals without magnetic storms. For the considered events, the substorm activity, as characterized by AE index, is found to be a necessary condition for the increase of relativistic electron fluxes, whereas a high solar wind speed alone is not sufficient for the relativistic electron growth. The enhancement of relativistic electron fluxes by 1.5–2 orders of magnitude is observed 1–3 days after the growth of the ULF index and VLF emission power. The growth of VLF and ULF wave powers coincides with the growth of substorm activity and occurs approximately at the same time. Both mechanisms operate at the first phase of electron acceleration. At the second phase of electron acceleration, the mechanism associated with the injection of electrons into the region of the magnetic field weakened by the ring current and their subsequent betatron acceleration during the magnetic field restoration can work effectively. Graphical Abstract

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Section: May-june 2017mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%