Average characteristics of high-energy magnetospheric electron flux enhancements and the parameters of near-Earth and interplanetary medium in 1987–2021

Abstract

ABSTRACT Based on the data of 35-yr (1987–2021) measurements of magnetospheric electron fluxes with energy >2 MeV in geostationary orbits, solar wind speed, and geomagnetic activity, a catalogue of electron flux enhancements was compiled in which the electron fluence exceeds 108 cm–2 sr–1 d–1. The epoch superposition method performed using the GOES-13 spacecraft data shows that large electron flux enhancements are preceded by a significant increase in the solar wind velocity and the Ap index of geomagnetic activity, and immediately before the increase the relativistic electron flux decreases. For the events of the catalogue, the average characteristics of electron flux enhancements and parameters of the interplanetary and near-Earth medium were calculated: the mean values of the diurnal and total fluences during an event and the average duration of electron enhancements. The average duration of the electron flux enhancement is 5 d, and the maximum duration is 24 d. Based on the calculated mean values of the electron fluences, solar wind velocity, and Ap-index of geomagnetic activity on the day of electron enhancement and on previous days, a typical behaviour of these parameters during and before an electron flux enhancement was obtained. The average characteristics of electron flux enhancements and the parameters of interplanetary and near-Earth medium are calculated before large electron flux enhancements, when the fluence exceeds 3 × 108, 5 × 108, and 109 particles cm–2 sr–1 d–1, respectively. It is shown that the greater the increase in solar wind velocity and geomagnetic activity the larger the subsequent electron flux enhancement.