Lifetimes of Relativistic Electrons as Determined From Plasmaspheric Hiss Scattering Rates Statistics: Effects of ωpe/Ωce and Wave Frequency Dependence on Geomagnetic Activity. Issue 13 (3rd July 2020) - Agapitov, O.
Abstract: Whistler‐mode hiss waves generally determine MeV electron lifetimes inside the plasmasphere. We use Van Allen Probes measurements to provide the first comprehensive statistical survey of plasmaspheric hiss‐driven quasi‐linear pitch‐angle diffusion rates and lifetimes of MeV electrons as a function of L *, local time, and AE index, taking into account hiss power, electron plasma frequency to gyrofrequency ratio ω pe /Ω ce, hiss frequency at peak power ω m, and cross correlations of these parameters. We find that during geomagnetically active periods with hiss observations, ω pe /Ω ce and ω m decrease, leading to faster electron loss. We demonstrate that spatiotemporal variations of ω m and ω pe /Ω ce with AE, together with wave power changes, significantly affect MeV electron loss, potentially leading to short lifetimes of less than 1 day. A parametric model of MeV electron lifetime driven by AE for L > 2.5 up to the plasmapause is developed and validated using Magnetic Electron Ion Spectrometer (MagEIS) electron flux decay database. Key Points: Statistical maps of plasmaspheric hiss wave power and frequency, plasma density are provided based on Van Allen Probes 2012–2018 EMFISIS data MeV electron lifetimes decrease ~1.5–2 times during disturbed periods due to decreased ω pe /Ω ce as compared with statistical average values A MeV electron lifetime model (including hiss amplitude, frequency, ω pe /Ω ce ) is presented and validated with the MagEIS electron lifetime database