Impact of Significant Time‐Integrated Geomagnetic Activity on 2‐MeV Electron Flux

Abstract

AbstractWe explore the impact on the outer radiation belt of significant time‐integrated ap events of continuously elevated geomagnetic activity, making use of Van Allen Probes measurements in 2013–2017. We show that most high peaks of 1.8‐MeV electron flux occur during the 10 days immediately following such events, with stronger events leading to higher flux. Events larger than 800 nT·hr are always followed by a high peak of flux in the heart of the outer radiation belt. They lead to 10‐day‐averaged 1.8‐MeV electron fluxes of the order of 106 e/cm2/sr/s/MeV in this region and 8×104 e/cm2/sr/s/MeV near geostationary orbit. Accordingly, they can be considered as reliable precursors of high peaks of 2‐MeV electron flux throughout the outer belt. We demonstrate that the flux peaks following such significant events can be parameterized by different geomagnetic indices at different radial locations in 2013–2017. Comparisons between the corresponding modeled flux peaks and observations show a reasonable agreement for both the timing, duration, and level of the peaks with 2015 data from the Van Allen Probes and also with 2002–2012 data from Global Positioning System satellites and 2003–2016 data from Geostationary Operational Environmental Satellites, provided that dropouts are taken into account via an appropriate threshold on solar wind dynamic pressure.