Characteristics of Energetic Electron Precipitation Estimated from Simulated Bremsstrahlung X-ray Distributions

Abstract

Determination of the fluxes and spectra of energetic particle precipitation into the Earth's atmosphere is of critical importance for radiation belt dynamics, magnetosphere-ionosphere coupling, as well as atmospheric chemistry. To improve the assessments of precipitating electrons using X-ray measurements requires deeper understanding of bremsstrahlung production, transport, and redistribution throughout the atmosphere. Here we use first-principles Monte Carlo models to explore relativistic electron precipitation events from the perspective of bremsstrahlung X-rays. The spatial distribution of X-rays is quantified from the ground level up to satellite altitudes. We then simulate X-ray images that would be captured using an ideal camera and calculate the energy spectra of X-rays originating from monoenergetic beams of precipitating electrons. Moreover, we show how these impulse responses to monoenergetic beams can be used to reconstruct the precipitating source using an inversion technique. Modeling results show that space-borne measurements of backscattered X-rays provide a promising method to estimate precipitation spatial size, fluxes, and spectra.