Probing the solar wind-inner magnetospheric coupling: validation of relativistic electron flux models

High fluxes of relativistic electrons in the inner magnetosphere have been associated with a range of spacecraft anomalies, and therefore the modeling of the flux is of direct relevance to the development of space weather applications. Time variations of the electron flux at a given L shell are ultimately functions of interplanetary parameters as well as of internal magnetospheric dynamics. It is important to resolve which one of the two elements is important for modeling and to what extent. To that end we compare two models of the magnetospheric relativistic electron flux at 2–6MeV spanning the range L 1⁄4 1–10 and driven by the solar wind plasma velocity, VSW. The finite-impulse-response (FIR) model represents the coupling of the flux to the solar wind velocity. It is part of an empirical model chain currently in development at the Center for Integrated Space Weather Modeling. The autoregressive moving-average (ARMA) model also includes a representation of the internal flux dynamics. The comparison is quantified in terms of the prediction accuracy, its variation with season and solar cycle phase, and its dependence on activity level. We find that the FIR model is more accurate than the ARMA model in most radial regions of the radiation belts, including the geosynchronous orbit. The results indicate that the long memory of the FIR model to past solar wind velocity inputs is more important in representing the effective coupling than ARMA’s additional internal dynamics. r 2004 Published by Elsevier Ltd.