Study of the North West Cape electron belts observed by DEMETER satellite

Abstract

[1] We analyzed observation data collected by the Instrument for the Detection of Particles (IDP) on board the DEMETER satellite during a period of 17 months in 2007 and 2008. In the meantime, the VLF transmitter located at North West Cape (NWC) ground station was shut down during 7 months and working for a total of 10 months. By an (on-off) method, our analysis for the first time revealed in detail the transient properties of the space electron precipitation belt which is induced by the man-made VLF wave emitted from NWC. We mapped the electron flux distribution and figured out the space regions that the NWC belt covered. The NWC electron spectrograms have been investigated in a wide range of the McIlwain parameter L (1.1-3.0). Furthermore, we obtained the averaged energy spectra of the NWC electrons within the drift loss cone and compared their characteristics during daytime and nighttime. Our results confirm the previous studies of the enhancement of NWC electrons, the wisp structure, and the day/night difference of the electron flux. In addition, more detailed information is provided. We provide not only evidence of a momentary flux enhancement up to 3 orders of magnitude but also a flux reduction at higher L shells with a maximum up to 60% of the original value. For the first time, the energy spectra of NWC electrons covering the entire IDP energy band are presented for both nighttime and daytime and are quantitatively compared. At the end, our results are discussed, and their agreement with the theory of wave-particle interactions is checked.

Terrestrial VLF transmitter injection into the magnetosphere

“…The MSK bandwidth necessarily covers the entire spectrum over a ∼200 Hz range. NWC is currently the only significant VLF transmitter south of the equator, but may also have the most impact on the radiation belts due in large part to its location [ Kulkarni et al , 2008; Li et al , 2012]. In many of the subsequent figures, we thus focus on NWC as a representative example due to the particularly intense signal (1 MW radiated power) and resulting high SNR.…”

Observed Propagation Route of VLF Transmitter Signals in the Magnetosphere

“…Ground‐based VLF transmitters have been utilized for long‐distance communication and geo‐location in past decades (Swanson, ; Watt, ) and can penetrate through the ionosphere and propagate within the plasmasphere. The related ionosphere disturbances, particle precipitation, wisp electron precipitation structure (Sauvaud et al, ), heating phenomenon, and wave propagation have also been studied (Bell et al, ; Cohen & Inan, ; Gamble et al, ; Graf et al, ; Inan et al, ; Li et al, ; Marshall et al, ; Parrot et al, , ; Starks et al, ; Tao et al, ).…”

A study on the energetic electron precipitation observed by CSES

“…Many scholars (Sauvaud et al, ; Gamble et al, ; Li et al, ) have studied the electron precipitation phenomenon—the two easterly‐westerly stripes at middle latitudes in both the northern and southern hemispheres (Figure ), which appear as wisp structures in the orbital energy spectrum. The number of electrons with energy between 100 and 600 keV are obviously increased, which tallies with the theory of linear wave‐particle interaction.…”

“…With the rapid development of satellite exploring technology, it has been determined from satellite observations that man‐made ground sources can definitely cause energetic particle precipitation in space. Some examples are: the EXOS‐B satellite observed the 0.3–6.9 keV electron flux anomaly caused by the electromagnetic waves of 0.3–9 kHz from the SIPLE station (Kimura et al, ); the low‐probability electron flux anomaly created by switching on/off the NPM transmitter was observed by the DEMETER satellite (Inan et al, ; Graf et al, ); and the DEMETER satellite also observed the electron precipitation belt ( L =1.4–1.7) correlated to the Australian NWC transmitter (Li XQ et al, ).…”