Quantifying the Drivers of Electron Loss from the Earth’s Radiation Belts: Lightning Generated Whistler Waves and Coulomb Energy Drag

Abstract:

We use observations from the Van Allen Probes, together with electron lifetime calculations from quasilinear diffusion modeling, to identify and quantify the drivers of electron precipitation from the Earth’s inner radiation belt and slot region. We build on our recent work that examined the role of ground-based Very Low Frequency (VLF) transmitter waves in precipitating electrons from the inner belt, which was demonstrated to exhibit a bifurcated structure (two-belt inner zone) due to the action of the VLF transmitter waves. We present new results that explicitly account for the role of lightning-generated whistler (LGW) waves in the electron lifetime calculations, using a statistical database of LGW waves recently obtained from the Van Allen Probes. In addition to these calculations of electron precipitation via quasilinear wave-particle interactions, we also consider a revised formulation of Coulomb scattering and examine the role of Coulomb energy drag in reducing the electron lifetimes. The theoretical calculations and modeling results are compared with observed electron decay rates to identify the physical processes most relevant for radiation belt electron precipitation.