Eects of a Mid-Latitude Solar Eclipse on the Thermosphere and Ionosphere- A Modelling Study

Abstract. A modelling study is presented which inves-tigates in-situ generated changes of the thermosphere and ionosphere during a solar eclipse. Neutral temperatures are expected to drop by up to 40 K at 240 km height in the totality footprint, with neutral winds of up to 26 m/s re-sponding to the change of pressure. Both temperatures and winds are found to respond with a time lag of 30 min after the passing of the Moon’s shadow. A gravity wave is gen-erated in the neutral atmosphere and propagates into the opposite hemisphere at around 300 m/s. The combined ef-fects of thermal cooling and downwelling lead to an overall increase in [O], while [N2] initially rises and then for sev-eral hours after the eclipse is below the "steady state " level. An enhancement of [NmF2] is found and explained by the atmosphere’s contraction during, and the reduced [O]/[N2] ratio after the eclipse