Ionospheric and thermospheric responses to the high-latitude solar eclipse on 10 June 2021

Abstract

A solar eclipse provides a rare opportunity to study upper atmospheric dynamics, including electrodynamics and coupling processes in the modified ionosphere and thermosphere system, where reduced solar radiation forces changes in the concentration, temperature, and natural wind. We present a multi-instrumental observational study of the high-latitude solar eclipse on June 10, 2021, using simultaneous measurements from incoherent scatter radars, GNSS satellites, and the GRACE-Follow-On satellite. We observed eclipse-induced electron density depletion and recovery in GNSS TEC observations over the European high latitude. Interestingly, the largest TEC depletion displayed a delayed response to the maximum solar obscuration. We used height-resolved measurements of plasma parameters to investigate their altitude variation and relation to TEC. We show that the depletion and recovery profiles of the electron temperature were consistent with the eclipse path across a wide range of F-region altitudes, while the electron density at higher altitudes showed delayed responses and persistent depletion after the maximum solar obscuration, which may explain the delayed behavior of GNSS TEC. Additionally, we show a concurrent decrease in the thermospheric neutral mass density by a few tens of percent from GRACE-FO satellite measurements in the polar region during the eclipse. We discuss how the depleted neutral density may further prolong the TEC recovery time.