Altitude Variations in Ionospheric Responses and Prolonged TEC Recovery During the High Latitude Solar Eclipse of 10 June 2021

A solar eclipse leads to a local decrease in ionospheric density that generally follows the solar obscuration function, whereas the density recovery phase is often characteristically prolonged after the eclipse ended. By using simultaneous measurements of the European Incoherent Scatter Scientific Association incoherent radar and GNSS during the solar eclipse on 10 June 2021, we study the altitude variation of ionospheric plasma parameters during eclipse-induced depletion and recovery processes in total electron content (TEC). The depletion and recovery profiles of the electron temperature are consistent with the eclipse path across a wide range of F-region altitudes, whereas the electron density at higher altitudes shows delayed responses and persistent depletion after the maximum solar obscuration. We show that this altitude asymmetry causes the eclipse-induced TEC depletion to persist for at least a few hours in the post-eclipse period. Our results indicate that the plasma pressure gradient and subsequent density diffusion account for the delayed response and the persistent density depletion. We also found a concurrent decrease in the thermospheric neutral mass density from in situ satellite measurements which may further prolong the TEC recovery time.