IGPP Seminar Series

Physical models of the near-Earth radiation environment

by Scot Elkington
LASP, University of Colorado


The Van Allen radiation belts consist of energetic electrons and ions trapped in the geomagnetic field. This region of space is of particular significance due to the large number of spacecraft operating at these altitudes, and global society's increasing reliance on space-based platforms for communications, navigation, weather prediction, and a variety of other economic and geopolitical purposes. Energetic electron fluxes in this region can vary orders of magnitude over a variety of time scales, and spacecraft operating here have sometimes been found susceptible to "anomalies" related to changes in the local radiation environment. Physical models of the radiation belt seek to simulate and predict variations in the space radiation environment based on first-principles views of the particle dynamics, making necessary approximations to turn complex field and particle interactions into computationally tractable problems. For example, global magnetohydrodynamic (MHD) models of the magnetosphere provide large-scale views of the interactions of the solar wind with the geomagnetic environment; coupling these global models with test particle simulations provides one means of examining aspects of the evolution of the radiation belts under complex driving conditions. Similarly, diffusive simulations of the radiation belts, based on Fokker-Planck formalisms, provide computationally-efficient methods of examining radiation belt dynamics where the transport coefficients are known or can be estimated. In this work we examine how these physical models of the radiation belts can be used synergistically to not only provide global snapshots of the space radiation environment, but also provide insight into the basic physical processes leading to changes in the radiation belts. We discuss the importance of boundary conditions in such simulations, and demonstrate how real-time observations of the outer zone radiation belts may be used in combination with physical models to provide realistic nowcasting of radiation belt fluxes in near-Earth space.
Tuesday, 24 February 2009
3853 Slichter Hall
Refreshments at 3:45 PM
Lecture at 4:00 PM