Variations of 0.7–6.0 MeV electrons at geosynchronous orbit as a function of solar wind

Abstract

The variations of MeV electron flux at geosynchronous orbit are predictable based on solar wind measurements. Using a model based on the standard radial diffusion equation applied for the years 1995–1999, a prediction efficiency of 64.4% and a linear correlation of 0.81 were achieved for the logarithm of average daily flux of 0.7–1.8 MeV electrons. The same model with different parameters gave a prediction efficiency of 70.2% and 72.4% and a linear correlation of 0.84 and 0.85, respectively, for 1.8–3.5 MeV and 3.5–6.0 MeV electrons during the same time period. The radial diffusion coefficient in the model is a function of location, solar wind velocity, interplanetary magnetic field, season, and solar cycle. The average lifetime of the electrons is a function of the radial distance and solar cycle. The radial diffusion equation is solved with given boundary conditions. These results suggest that MeV electrons at geosynchronous orbit, extending over a wide energy range, have a systematic response to the solar wind variations. This model has been updated and is making real‐time forecasts of daily averaged >2 MeV electron fluxes at geosynchronous orbit.