Simultaneous Observations of Topside Mid‐Latitude Plasma Troughs and Subauroral Red Arcs: The Role of Electron Heat Conduction

Abstract Topside plasma troughs in the mid‐latitude ionosphere, accompanied by enhancements in electron temperature and the occurrence of subauroral red arcs, were observed by the Swarm‐B satellite and co‐located airglow measurements. To investigate the underlying physical processes, we developed a two‐dimensional numerical simulation model incorporating a non‐equilibrium energy equation, with particular emphasis on the roles of topside electron heat conduction and the resulting ambipolar diffusion. The key observational features of both plasma density and electron temperature were successfully reproduced by assuming a Gaussian‐shaped topside heat flux. Simulation results indicate that the observed plasma trough along the Swarm‐B orbit is likely driven by a transient enhancement of plasmaspheric heat flux. Additionally, the influences of meridional winds and ion composition on the asymmetry of the trough were found to be negligible. These findings underscore the critical role of plasmaspheric energy input in modulating ionospheric structures, identifying variations in electron heat flux as the primary driver. This study advances the understanding of mid‐latitude trough dynamics by linking magnetospheric energy transport processes to ionospheric plasma depletion, with important implications for space weather modeling and forecasting.