Investigation of NWC-induced electron precipitation and theoretical simulation

TL;DR

This study reports the first observation of NWC-induced electron precipitation in the 30-100 keV range, expanding understanding of VLF wave interactions with electrons in the inner radiation belt through satellite data and theoretical modeling.

Contribution

It introduces new observations of 30-100 keV electron flux enhancements caused by NWC VLF transmitter, supported by theoretical simulations and ray tracing analysis.

Findings

30-100 keV electrons are primarily east of the transmitter

Electron distribution varies with L-shell, decreasing at higher energies

Satellite observations agree with wave-particle interaction theory

Abstract

Enhancement of the electron fluxes in the inner radiation belt, which is induced by the powerful North West Cape (NWC) very-low-frequency (VLF) transmitter, have been observed and analyzed by several research groups. However, all of the previous publications have focused on NWC-induced >100-keV electrons only, based on observations from the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) and the Geostationary Operational Environmental Satellite (GOES) satellites. Here, we present flux enhancements with 30--100-keV electrons related to NWC transmitter for the first time, which were observed by the GOES satellite at night. Similar to the 100--300-keV precipitated-electron havior, the low energy 30--100-keV electron precipitation is primarily located east of the transmitter. However, the latter does not drift eastward to the same extent as the former, possibly because of the lower electron velocity. The 30--100-keV electrons are distributed in the L=1.8--2.1 shell range, in contrast to the 100--300-keV electrons which are at L=1.67--1.9. This is consistent with the perspective that the energy of the VLF-wave-induced electron flux enhancement decreases with higher L-shell values. We expand upon the rationality of the simultaneous enhancement of the 30--100- and 100--300-keV electron fluxes through comparison with the cyclotron resonance theory for the quasi-linear wave-particle interaction. In addition, we interpret the asymmetry characteristics of NWC electric power distribution in north and south hemisphere by ray tracing model. Finally, we present considerable discussion and show that good agreement exists between the observation of satellites and theory.