Scaling laws for the inner structure of the radiation belts

Abstract

Accurately modeling the evolution of the electron radiation belts within the plasmasphere represents both an imperative goal for space weather forecasting and a great challenge. Combining previously developed approximate analytical expressions of electron lifetimes with recent statistical models of plasma density, ULF, whistler-mode, and electromagnetic ion cyclotron waves, we demonstrate that geomagnetic activity and plasma density actually govern the inner structure of the radiation belts through several simple analytical scaling laws when Kp < 3. Many of the observed characteristic features of electron fluxes in the energy versus L shell parameter space are straightforwardly explained. In particular, the upper energy limit of significant electron fluxes at L = 1.5 is estimated as ∼1 MeV in agreement with recent satellite observations. This approximate analytical model represents a very simple and powerful tool for exploring and better understanding the complex variations of the inner structure of the radiation belts with geomagnetic activity during relatively quiet times.