Extension of an Empirical Electron Flux Model From 6 to 20 Earth Radii Using Cluster/RAPID Observations

Abstract

AbstractAn existing empirical model of the electron fluxes at geosynchronous orbit is extended radially outward in the equatorial plane to ~6–20 Earth radii (RE) using observations from the Research with Adaptive Particle Imaging Detectors (RAPID) instrument on the Cluster spacecraft. The new model provides electron flux predictions in the energy range ~45 eV to ~325 keV, as a function of local time and radial distance from the Earth, with geomagnetic activity parameterized by the Kp index. The model outputs include the mean and median electron fluxes along with the standard deviation and the 5th, 25th, 75th, and 95th percentiles for the given input conditions. The flux outputs from the model are tested against in‐sample observations from Cluster/RAPID and out‐of‐sample observations from Time History of Events and Macroscale Interactions during Substorms (THEMIS)/Solid State Telescope with good prediction efficiency during quiet and active intervals, as quantified by standard methods. This new model is intended to supplement current predictive capabilities in the magnetosphere for spacecraft operations, as well as providing the necessary boundary and/or input conditions for computational/physical models of the magnetospheric system when the necessary in situ observations are unavailable. While the new model can certainly not reproduce the rapid small‐scale fluctuations inherent in spacecraft observations, it does provide a coarse capability to predict the flux of electrons close to the equatorial plane, based on radial distance, energy, local time, and geomagnetic activity, in regions where no in situ assets are available.