The Response of Geomagnetic Daily Variation and Ionospheric Currents to the Annular Solar Eclipse on 21 June 2020

Abstract

In this study, we examined the response of geomagnetic daily variation and ionospheric currents to the solar annular eclipse that passed through China at 10:00–17:30 LT on 21 June 2020. We utilized geomagnetic field data obtained from the Geomagnetic Network Center of China, Institute of Geophysics, China Earthquake Administration and International Real-time Magnetic Observatory Network, which extend from middle latitudes to equatorial regions in China and surrounding areas. It is found that the eclipse obscuration reduces the intensity of geomagnetic daily variation at most stations as compared with the 5-quiet-day average. The response of geomagnetic daily variation to the solar eclipse depends on local time and latitude. In most shadowed areas of the eclipse, there is a reduction of northward (southward) component of the meridional magnetic daily field (ΔX) below (above) ∼30° magnetic latitudes. The solar eclipse can also induce a decrease of the zonal magnetic field variation (ΔY). Meanwhile, we observed that the solar eclipse reduces the intensity of vertical geomagnetic component (ΔZ) at the stations around the early afternoon aside the eclipse totality. In general, these geomagnetic responses imply that the solar eclipse can reduce the ionospheric solar quiet (Sq) current system. These ionospheric currents and ground geomagnetic field disturbances during the solar eclipse are also verified by a global physical model. The simulation demonstrates that the ionospheric currents in the southern hemisphere, where the solar eclipse does not cover, also have a weak response. Overall, the ionospheric current disturbance induced by the solar eclipse shows a counter-Sq pattern.