Energetic Electron Precipitation From the Radiation Belts: Geomagnetic and Solar Wind Proxies for Precipitation Flux Magnitudes

Previously the geomagnetic Ap index has been used as a proxy to produce empirical energetic electron precipitation (EEP) forcing representations suitable for incorporation into coupled-climate model runs. The long-running Ap index has the advantage that it allows descriptions of EEP to be made for periods outside the current satellite era, but its suitability has not been checked against other reasonable proxies. In this study three different satellite electron precipitation data sets (DEMETER, POES, and SAMPEX) are used to examine the suitability of a variety of geomagnetic and solar wind proxies to represent EEP flux in different energy ranges. Analysis was undertaken using indices at their fundamental timescales (typically minutes or hours). For medium energy electron precipitation (i.e., >100 keV), the best proxy is found to be either Ap or Dst. For relativistic energy electron precipitation (i.e., >700 keV), the best proxy is Kp or AE, the latter suggesting a connection to substorm activity. The identification of the Ap index as one of the best proxies for medium energy EEP supports the approach taken by van de Kamp et al. (2016), https://doi.org/10.1002/2015jd024212. An EEP forcing capability based on Ap was developed by those authors for inclusion as a solar forcing factor in the Coupled Model Intercomparison Project Phase 6 of the World Climate Research Program.