Study of the NWC electrons belt observed on DEMETER Satellite

TL;DR

This study analyzed DEMETER satellite data over 17 months to investigate how man-made VLF waves from the NWC transmitter induce transient electron enhancements and losses in Earth's radiation belts, revealing detailed spatial and energetic properties.

Contribution

First detailed analysis of NWC VLF-induced electron dynamics, mapping flux distribution, energy spectra, and day-night differences in the radiation belt region.

Findings

VLF emissions cause electron flux enhancements up to 1000 times.

Electron loss can reach up to 60% in higher L shells.

Daytime electron spectra are more attenuated than nighttime spectra.

Abstract

We analyzed observation data collected by the Instrument for the Detection of Particles (IDP) on board of DEMETER satellite during the period of total seventeen months in 2007 and 2008. In the meantime, the VLF transmitter located at NWC ground station was shutdown for seven months and working for total ten months. Our analysis, for the first time, revealed in details the transient properties of the space electrons induced by the man-made VLF wave emitted by the transmitter at NWC. First, we mapped the electron flux distribution and figured out the special range what the NWC belt covered. Then we investigated the NWC electron spectrograms in a wide range of McIlwain parameter (up to L=3.0). Finally, we obtained the averaged energy spectrum of the NWC electrons within the drift loss-cone, and compared the difference during the observations between daytime and nighttime. Our results proved the fact that the VLF emissions from NWC transmitter created momentary electron enhancement with fluxes up to 3 orders of magnitude. These electrons are distributed in the region of 180 degree in longitude and 1.6 ~ 1.9 of L shell. In addition, the VLF emission induced either enhancement or loss of electrons in higher magnetic shells up to L=3, and the maximum loss was up to 60% of the original value. The energy spectra of these electrons revealed that the enhancement during the NWC daytime are more attenuated than those in the NWC nighttime, and that the shape and the cutoff energy of the spectra are also quite different. We will present the results of our analysis, compare it with previous studies, and discuss the agreement of our results with the theory of wave-particle interaction.