Lifetimes of Relativistic Electrons as Determined From Plasmaspheric Hiss Scattering Rates Statistics: Effects of ωpe/Ωce and Wave Frequency Dependence on Geomagnetic Activity

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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 ωpe/Ωce, hiss frequency at peak power ωm, and cross correlations of these parameters. We find that during geomagnetically active periods with hiss observations, ωpe/Ωce and ωm decrease, leading to faster electron loss. We demonstrate that spatiotemporal variations of ωm and ωpe/Ωce 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.
Notes
Year of Publication
2020
Journal
Geophysical Research Letters
Volume
47
Number
Number of Pages
e2020GL088052
Date Published
05/2020
URL
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL088052
DOI
https://doi.org/10.1029/2020GL088052