Radiation belt electron precipitation due to VLF transmitters: Satellite observations

Abstract

[1] In the Earth's inner magnetosphere, the distribution of energetic electrons is controlled by pitch-angle scattering by waves. A category of Whistler waves originates from powerful ground-based VLF transmitter signals in the frequency range 10 -25 kHz. These transmissions are observed in space as waves of very narrow bandwidth. Here we examine the significance of the VLF transmitter NWC on the inner radiation belt using DEMETER satellite global observations at low altitudes. We find that enhancements in the $100 -600 keV drift-loss cone electron fluxes at L values between 1.4 and 1.7 are linked to NWC operation and to ionospheric absorption. Waves and particles interact in the vicinity of the magnetic equatorial plane. Using Demeter passes across the drifting cloud of electrons caused by the transmitter; we find that $300 times more 200 keV electrons are driven into the drift-loss cone during NWC transmission periods than during non-transmission periods. The correlation between the flux of resonant electrons and the Dst index shows that the electron source intensity is controlled by magnetic storm activity.

The Energetic Particle Telescope: First Results

“…Such low fluxes in the Northern hemisphere were also observed by DEMETER orbiting at an altitude of 700 km (Sauvaud et al 2008(Sauvaud et al , 2013, as well as by the FEIO detector onboard the SAC-D satellite (S. Bourdarie, personal communication 2014). This is a consequence of the tilt and excentricity of the geomagnetic field line distribution which, at these longitudes, lifts the mirror points of trapped particles at higher altitudes in the Northern hemisphere than in the Southern one where the surface field intensity is significantly reduced.…”

Burst increases of precipitating electrons recorded by the DEMETER satellite before strong earthquakes

“…Additionally, a decrease in the particle flux over this seismic region, accompanied by electrostatic turbulence, was observed during the next orbit passing over the epicenter area during the daytime. Furthermore, Sauvaud et al (2008) investigated for a relationship between energetic electrons and ground-based VLF transmitter signals and reported enhancements in the ∼100-600 keV drift-loss cone electron fluxes at L values between 1.4 and 1.7 being due to the Australian NWC operations and ionospheric absorption. Gemelos et al (2009) reported that seasonal variations in energetic electrons were consistent with lighting-induced electron precipitation (LEP) over North America.…”

Scattering of Magnetic Mirror Trapped Fast Electrons by a Shear Alfvén Wave

“…Because the trapped energetic charged particles from such events pose severe hazards to expensive space satellites, there is a great deal of current interest on concepts that can lead to artificial remediation of the energetic trapped particles [18]. One example is enhancing electron precipitation by injecting whistler mode VLF waves in the inner radiation belt [19] [20]. In this letter, we report the first clear demonstration of the scattering of energetic, magnetic mirror trapped electrons by Shear Alfvén Waves (SAW) in a lab experiment.…”