Van Allen Probes Bibliography is from August 2012 through September 2021 Notice:
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Relativistic electron pitch-angle scattering by electromagnetic ion cyclotron waves during geomagnetic storms
Author | Summers, D.; |
Keywords | Local Loss due to VLF/ELF/EMIC Waves |
Abstract | [1] During magnetic storms, relativistic electrons execute nearly circular orbits about the Earth and traverse a spatially confined zone within the duskside plasmapause where electromagnetic ion cyclotron (EMIC) waves are preferentially excited. We examine the mechanism of electron pitch-angle diffusion by gyroresonant interaction with EMIC waves as a cause of relativistic electron precipitation loss from the outer radiation belt. Detailed calculations are carried out of electron cyclotron resonant pitch-angle diffusion coefficients Dαα for EMIC waves in a multi-ion (H+, He+, O+) plasma. A simple functional form for Dαα is used, based on quasi-linear theory that is valid for parallel-propagating, small-amplitude electromagnetic waves of general spectral density. For typical observed EMIC wave amplitudes (1\textendash10nT), the rates of resonant pitch-angle diffusion are close to the limit of \textquotedblleftstrong\textquotedblright diffusion, leading to intense electron precipitation. In order for gyroresonance to take place, electrons must possess a minimum kinetic energy Emin which depends on the value of the ratio (electron plasma frequency/electron gyrofrequency); Emin also depends on the properties of the EMIC wave spectrum and the ion composition. Geophysically interesting scattering, with Emin comparable to 1 MeV, can only occur in regions where (electron plasma frequency/electron gyrofrequency) >=10, which typically occurs within the duskside plasmapause. Under such conditions, electrons with energy >=1 MeV can be removed from the outer radiation belt by EMIC wave scattering during a magnetic storm over a time-scale of several hours to a day. |
Year of Publication | 2003 |
Journal | Journal of Geophysical Research |
Volume | 108 |
Number of Pages | |
Section | |
Date Published | 04/2003 |
ISBN | |
URL | http://onlinelibrary.wiley.com/doi/10.1029/2002JA009489/full |
DOI | 10.1029/2002JA009489 |