Publication Date:
2016-04-09
Description:
A flux dropout is a sudden and sizable decrease in the energetic electron population of the outer radiation belt on the timescale of a few hours. We simulated a flux dropout of highly relativistic 〉 2.5 MeV electrons using the Radiation Belt Environment (RBE) model, incorporating the pitch-angle diffusion coefficients caused by EMIC waves for the geomagnetic storm event of 23 – 26 October 2002. This simulation showed a remarkable decrease in the 〉 2.5 MeV electron flux during main phase of the storm, compared to those without EMIC waves. This decrease was independent of magnetopause shadowing or drift loss to the magnetopause. We suggest that the flux decrease was likely to be primarily due to pitch-angle scattering to the loss cone by EMIC waves. Furthermore, the 〉 2.5 MeV electron flux calculated with EMIC waves correspond very well with that observed from SAMPEX spacecraft. EMIC wave scattering is therefore likely one of the key mechanisms to understand flux dropouts. We modeled EMIC wave intensities by the Kp index. However, the calculated dropout is a several hours earlier than the observed one. We propose that Kp is not the best parameter to predict EMIC waves.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
