Coordinated Swarm and EISCAT Svalbard Radar observations of the cusp ionosphere

Abstract:

We present a case study involving the EISCAT Svalbard Radar (ESR) sounding the cusp ionosphere while the Swarm fleet flew through its beam. ESR data show strong electron temperatures, generally ascribed to soft electron precipitation, and a structured electron density possibly due to pulsed reconnection at the magnetopause. The particle sensors on board Swarm record much shorter-scale electron and ion structures, revealing the actual size of particle injection region and that of the corresponding region affected by enhanced convection. Magnetic field measurements also give us the field-aligned current (FAC) density, with which we infer the electron heating due to the thermoelectric effect in the upward FAC part. We are thus able to separate the contribution of the electron precipitation and that of the FAC, both responsible for the net heating of the ionospheric thermal electron population.