Proton precipitation from EMIC waves at high latitudes: A casestudy from 29 March 2021

Electron precipitation driven by electromagnetic ion cyclotron (EMIC) waves in the Pc1 range (0.1–5Hz) has been suggested as a significant loss mechanism for outer radiation belt fluxes of electrons in the 1–5 MeV energy range. Moreover, EMIC waves have been also observed to cause significant precipitation of ring current protons during geomagnetic storms.
In this study we report the concurrent observations of electromagnetic ion cyclotron Pc1 waves in both ionospheric F-region and at ground. Key event on March 29, 2021 shows that high latitude ground magnetometers in Antarctica and CSES LEO satellite detected concurrent Pc1 wave and energetic proton precipitation. In the ionospheric F-layer above the Auroral zone, the CSES satellites observed transverse Pc1 waves and localized plasma density enhancement, which is occasionally surrounded by wide/shallow depletion. This might indicate that EMIC wave-induced proton precipitation contributes to the energy transfer from the magnetosphere to the ionosphere and to the ionization of the F-layer.