GEM: Development of a Three-dimensional (3-D) Diffusion Code as a Radiation Belt Module in the Geospace General Circulation Model (GGCM)

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

This project will develop a Radiation Belt Module (RBM) for the Geospace environment Modeling (GEM) Geospace General Circulation Model (GGCM). The RBM will facilitate a major advance in our understanding of energetic electron non-adiabatic dynamics, since, for the first time, all dominant physical process, which affect radiation belt electrons, will be simultaneously evaluated. The RBM will be driven by the coupled Rice Convection Model (RCM) of the inner magnetosphere and magnetohydrodynamic (MHD) codes to describe the global magnetosphere. It will consequently provide the capability of predicting changes in the radiation belts based solely on solar disturbances. In the collisionless magnetospheric environment, wave particle interactions provide the dominant mechanism for pitch-angle scattering, energy diffusion and anomalous cross-field transport. The current understanding of such processes has now matured to a level where realistic quantitative models can be constructed. In the RBM, such processes will be quantified by 3-D diffusion coefficients, based on the anticipated power spectral density of scattering waves. Radial diffusion rates will be obtained from the properties of ULF waves simulated by the MHD code. A parameterization scheme for the global distribution of VLF waves and EMIC waves will be developed, based on the flux of injected ring current electrons and ions provided by the RCM. A quasi-linear diffusion code will be used to evaluate the rates of pitch-angle scattering and energy diffusion on a global scale. Numerical integration of the 3-D diffusion equation will provide a simulation of the response of radiation belt electrons to solar disturbances. The proposed study is central to three challenges in the 2002 NRC Decadal report: (1) Understanding the space environment of Earth and other solar system bodies and their dynamical response to external and internal influences, (2) Understanding the basic physical principals manifest in processes observed in solar and space plasmas, and (3) Developing near real-time predictive capability for understanding and quantifying the impact on human activities of dynamical processes at the Sun, in the interplanetary medium, and in the Earth's magnetosphere. The UCLA Visualization Portal facilities will be used to construct 3-D movies of the variability of radiation belt electrons during storms. Results from the study will be integrated into courses for a new Collaborative Laboratory and Space Plasma Physics Interdisciplinary Degree Program at UCLA, and will be shown at UCLA visualization portal for graduate students.