Direct Evidence of the Lower Atmosphere Perturbations Producing Abnormal Ionospheric Longitudinal Gradients During Quiescent Geomagnetic Conditions

Abstract

An unusual case of a large ionospheric longitudinal gradient in East Asia on 11 May 2021 occurred during a geomagnetically-quiet period. It shows the largest east-west difference in electron density at Yamagawa and Wuhan stations when Kp < 2 for 13:00–17:00 LT in 2021. Ground- and satellite-based observations consistently confirm that there was a decrease in the west and an increase in the east of ∼125°E, with hemispherical symmetric with respect to the geomagnetic equator. The potential mechanism is further investigated through multi-observations of plasma drifts and neutral winds, provided by the Ionospheric Connections Explorer satellite and newly-established Sanya Incoherent Scatter Radar. The prominent longitudinal gradient in plasma drifts, electro-dynamically coupled with E-region winds, is suggested as the contributor for the east-west differences, together with the strong gradient of F-region winds in phase. This study provides direct evidence linking atmosphere perturbations to unusual longitudinal structure of terrestrial space plasma environment.