It has long been recognized that during solar eclipses, the ionosphere-thermosphere system changes greatly within the eclipse shadow, due to the rapid reduction of solar irradiation. However, the concept that a solar eclipse impacts polar ionosphere behavior and dynamics as well as magnetosphere-ionosphere coupling has not been appreciated.

Polar maps of differential TEC (units: TECU) in the Northern Hemisphere as a function of geographic latitude and local time from (left) GPS observations and (right) TIEGCM simulations on 21 August 2017. For the observation, the differential TEC maps represent the differences between TEC data on 21 August 2017 and the monthly average of August 2017; for the simulations, they were obtained from the simulations with and without eclipse (with Eclipse - without Eclipse). The dashed lines in the right panels indicate the obscuration rate of the solar eclipse at each UT.

In this study, we investigate the potential impact of the 21 August 2017 solar eclipse on the polar tongue of ionization (TOI) using a high-resolution, coupled ionosphere-thermosphere-electrodynamics model (TIEGCM). The reduction of electron densities by the eclipse in the middle latitude TOI source region leads to a suppressed TOI in the polar region. The TOI suppression occurred when the solar eclipse moved into the afternoon sector. The GPS total electron content observations show similar tendency of polar-region TEC suppression. This study reveals that, a solar eclipse occurring at middle latitudes may have significant influences on the polar ionosphere and magnetosphere-ionosphere coupling.

Publication Name: Geophysical Research Letters

First HAO Author's Name: Wenbin Wang