Recent developments in the radiation belt environment model

Abstract

a b s t r a c tThe fluxes of energetic particles in the radiation belts are found to be strongly controlled by the solar wind conditions. In order to understand and predict the radiation particle intensities, we have developed a physics-based Radiation Belt Environment (RBE) model that considers the influences from the solar wind, ring current and plasmasphere. Recently, an improved calculation of wave-particle interactions has been incorporated. In particular, the model now includes cross diffusion in energy and pitch-angle. We find that the exclusion of cross diffusion could cause significant overestimation of electron flux enhancement during storm recovery. The RBE model is also connected to MHD fields so that the response of the radiation belts to fast variations in the global magnetosphere can be studied. We are able to reproduce the rapid flux increase during a substorm dipolarization on 4 September 2008. The timing is much shorter than the time scale of wave associated acceleration.Published by Elsevier Ltd.

Impact of Solar Wind on the Earth Magnetosphere: Recent Progress in the Modeling of Ring Current and Radiation Belts

“…The Radiation Belt Environment (RBE) model has been rigorously developed over past 10 years (Fok et al, 2005;Fok et al, 2011;Fok, Moore & Spjeldvik, 2001;Fok et al, 2008;Glocer et al, 2011;Zheng et al, 2011;. It models both the radiation belts and ring current electrons.…”

“…The model-data comparison is continually posted at http://mcf.gsfc.nasa.gov/RB_nowcast/. Fok et al (2011) study the effect of wave-particle interaction on radiation belt dynamics, including the effect of cross diffusion terms. Fig.4 shows simulated radiation belt fluxes on 23-27 October 2002 (adopted from Fig.2)) as a function from L and t. Two energy bins are considered: low energy part of radiation belts (may be considered also as ring current electrons) 20-70 keV and high energy radiation belt electrons 0.6-1.8 MeV.…”

“…Recently Fok et al (2011) andGlocer et al (2011) use coupled RBE-SWMF to examine 2 events with rapid radiation belt enhancements. Based on careful data analysis from Akebono, TWINS and NOAA satellites, Glocer et al (2011) conclude that the time scale of these enhancements is about 2 hours and thus it is too short for wave associated energization.…”

“…The example of flux enhancement is shown on the Fig. 5 (adapted from Fok et al (2011)). Panel (a) shows the Akebono electron flux of energy >2.5 MeV from September 3, 2008, 00 UT to September 4, 12 UT.…”

“…The Akebono data are averaged over 3 orbit periods (∼ 7.5 h). Fok et al (2011) andGlocer et al (2011) perform RBE-SWMF simulations to understand the cause of the flux enhancement seen in the Akebono electron data. Additionally, the RBE is run in stand-alone mode with empirical models as inputs.…”