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This study investigates the diurnal variation of topside ionospheric plasma density using the Ionospheric Connection Explorer (ICON) observations from May to July in 2020 and 2021. The total ion density exhibits daytime double‐maxima (DDM) patterns, also known as "bite‐out" at magnetic latitudes from 10°S to 20°N and longitudes of 180°–276°E, but a single peak in other longitudes. The total ion density between 180° and 276°E reaches its first peak around 12 LT (Local Time) in both hemispheres and the second peak at 14–15 LT in the Northern Hemisphere, gradually shifting to around 16–17 LT in the Southern Hemisphere. The formation of the first peak is mainly influenced by vertical plasma drift, while the second peak is associated with both neutral wind and vertical plasma drift. Furthermore, this study provides direct observational evidence for the influence of neutral winds on the longitude and latitude differences of the topside DDM. Stronger southward magnetic meridional winds and vertical plasma drifts are observed at approximately 11–15 LT in the longitude sector with DDM compared to other longitudes, leading to a valley of ion density in the Southern Hemisphere around 15 LT. In the Northern Hemisphere, ion density continues to accumulate to form a second peak at 15 LT. Key Points: Diurnal double maxima (DDM) occur in the daytime topside ionosphere around 180°–276°E in June SolsticeThis study presents probably evidence that neutral trans‐equatorial winds cause the formation of the topside ionospheric DDMSimulations analyzed the respective contributions of neutral winds and E × B drift to the topside ionospheric DDM [ABSTRACT FROM AUTHOR]

The state and variations of the Ionosphere‐Thermosphere (I‐T) system are strongly influenced by dynamical processes, with these effects being amplified during intense space environment disturbances such as geomagnetic storms, producing multi‐scale disturbance features in the I‐T system. The redistribution of energy and momentum through the dynamical processes is currently not well understood. Unfortunately, the dearth of thermospheric observations has yielded limited studies capable of monitoring and analyzing the I‐T dynamical coupling during storms using co‐located measurements. This work examines the responses of the I‐T system during the April 2023 geomagnetic storm based on high‐resolution continuous I‐T system observations at Mohe observatory, a middle latitude station. Both large‐scale features and short‐period oscillations were identified in multiple key parameters of the I‐T system. Similar disturbed patterns in thermospheric winds occurred during the main and recovery phases of the geomagnetic storm. However, the oscillation features in many parameters of the I‐T system are only observed during the main phase. The results of concurrent I‐T system observations unveil the oscillation features of thermospheric winds, temperatures, the ionospheric F2 peak height, electron density, and total electron content. These findings reveal the important influence of wind divergence on thermospheric temperature disturbances and its modulatory effect on ionospheric disturbances. Plain Language Summary: The upper atmosphere is partially ionized to form the ionosphere (I), and the neutral component of the background is known as the thermosphere (T), constituting the I‐T system. The state and variations of the I‐T system are strongly influenced by dynamical processes, especially during intense space weather events like geomagnetic storms. Investigating the response features of the I‐T system during geomagnetic storms would enhance our understanding of the mechanisms and impacts of dynamical processes. However, due to the limited thermospheric observation, most studies are unable to concurrently address the conditions of both the thermosphere and ionosphere, resulting in a nebulous understanding of the involved dynamical processes. Thus, this study investigates the responses of the I‐T system during the April 2023 geomagnetic storm by utilizing high‐resolution, continuous I‐T system observations obtained from the Mohe observatory. The observations identified disturbances on different space‐time scales in the I‐T system and unveiled the correlation between thermospheric wind, temperature, ionospheric peak height, electron density, and total electron content disturbances, revealing the crucial role of thermospheric wind in linking thermosphere and ionosphere disturbances through dynamical processes. Key Points: The multi‐scale ionospheric/thermospheric disturbances during geomagnetic storms were monitored by the co‐located observationsThe adiabatic compression process of the horizontal wind is an important factor for the traveling thermospheric temperature disturbanceIn addition to variation of ionospheric altitude caused by the meridional wind, the divergence of wind also modulates the amplitude of traveling ionospheric disturbancess [ABSTRACT FROM AUTHOR]