The Response of Geomagnetic Daily Variation and Ionospheric Currents to the Annular Solar Eclipse on 21 June 202

Abstract

According to the ampere's law, the geomagnetic variations caused by the ionosphere current can detect the ionosphere electrodynamic process during a solar eclipse. Due to the lack of observation, the previous research on the geomagnetic effect of solar eclipse focused on the range of one or several geomagnetic stations, which makes the latitude and local variation characteristics of the geomagnetic effect and the corresponding ionosphere electrodynamics process are not totally studied. The annular solar eclipse on June 21,2020 passed through China during the daytime, and the regional high density observation of the Geomagnetic Network Center of China, Institute of Geophysics, China Earthquake Administration and International Real-time Magnetic Observatory Network provides a good opportunity for the study of this issue. In this work, we studied the latitude and local time dependences of the geomagnetic-solar eclipse effect of the June 21,2020 annular eclipse event in China and the neighbour areas, and analyzed the electrodynamics process of the ionosphere. The results are as follows: The eclipse weakens the intensity of three components for the geomagnetic daily variations. Among them, the effect of the north-south component ΔX has a clear latitude dependence, that is, the decrease of intensity significantly below the center of the Sq current vortex and is slightly weaker above the focus, while the eclipse effect of ΔX near the center of the current vortex is almost absent. In addition, the effect of the east-west component ΔY increases as latitude decreases and the eclipse obscuration rate increases . The eclipse effect of ΔY along the totality from noon to afternoon shows a local time dependent, while the eclipse effect of ΔX component is not so regular like ΔY, it is roughly stronger from early afternoon to early afternoon than that in the late afternoon. The eclipse effect of the vertical component ΔZ was weak, mainly in the early afternoon period on the totality path. The eclipse effects of the geomagnetic daily variation simulated by the TIEGCM are generally consistentwith those by the ground magnetometer data. It was demonstrated that the ionospheric current system caused by the eclipse has a counter-Sq pattern and thus weakens the background Sq current system.   Keywords: Geomagnetic Daily Variation, Ionospheric Currents, Solar Eclipse