Radiation belt electron flux variability during three CIR-driven geomagnetic storms

Coronal holes produce high speed solar wind streams (HSS) that subsequently interact with the slower downstream solar wind forming co-rotating interaction regions (CIRs). The CIR/HSS combination drives geomagnetic storms that have a weak to moderate signature in Dst. We simulate the behavior of relativistic (976 keV) electrons in the outer radiation belt and the slot region (2less-than-or-equals, slantLless-than-or-equals, slant7) during three CIR-driven storms associated with three consecutive rotations of a coronal hole that occurred just after solar maximum during June–August 1991. We use a 1d radial diffusion model (RADICAL) with losses due to pitch-angle scattering by plasmaspheric hiss. The losses are expressed through the electron lifetime calculated using the PADIE code driven by a global Kp-dependent model of plasmaspheric hiss intensity and fpe/fce. The outer boundary condition is time and energy-dependent and derived from observations. The model reproduces the observed flux at L=5 to within about a factor of 3 suggesting that flux levels are well-described by radial diffusion to and from the outer boundary. At L=3.5 and 4, the model overestimates the flux decay rates. This results in the observed flux exceeding the model flux, by up to a factor of 5 at L=4 and by up to a factor of 8 at L=3.5, by the end of the recovery phase. Comparison with model results from a geomagnetically quieter interval suggest that the underestimation in flux may be due to the lack of representation of local wave acceleration in the model.


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Authors: Lam, M. M. ORCIDORCID record for M. M. Lam, Horne, R. B. ORCIDORCID record for R. B. Horne, Meredith, N. P. ORCIDORCID record for N. P. Meredith, Glauert, S. A. ORCIDORCID record for S. A. Glauert

On this site: Mai Mai Lam, Nigel Meredith, Richard Horne, Sarah Glauert
1 January, 2009
Journal of Atmospheric and Solar-Terrestrial Physics / 71
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