Quantitative forecast of relativistic electron flux at geosynchronous orbit based on low‐energy electron flux

Abstract

A strong correlation between the behavior of low‐energy (tens to hundreds of keV) and high‐energy (>1 MeV) electron fluxes measured at geosynchronous orbit has been discussed, and this correlation is further enhanced when a time offset is taken into account. A model has been developed incorporating this delay time between similar features in low‐ and high‐energy electron fluxes to forecast the logarithm of daily averaged, 1.1–1.5 MeV electron flux at geosynchronous orbit several days in advance. The model uses only the current and previous days' daily averaged fluxes of low‐ and high‐energy electrons as input. Parameters in the model are set by optimizing prediction efficiency (PE) for the years 1995–1996, and the optimized PE for these 2 years is 0.81. The model is run for more than one full solar cycle (1995–2006), and it consistently performs significantly better than a simple persistence model, where tomorrow's forecasted flux is simply today's value. Model results are also compared with an inward radial diffusion forecast model, in which the diffusion coefficient is a function of solar wind parameters. When the two models are combined, the resulting model performs better overall than each does individually.