Formation of Storm-enhanced density during April 2023 Storm Using GITM-SAMI3

Ionospheric density variation affects the propagation of radio signals, such as the Global Navigation Satellite System (GNSS) signals and over-the-horizon radar communication. Those effects are more prominent during active geomagnetic conditions, under which important high-density ionospheric structures with large density gradients can developed. Storm-enhanced densities (SEDs) are mainly observed in the mid-latitudes and subauroral regions during geomagnetic storms. It is well known that SEDs would be an important reservoir for other high-latitude ionospheric features, such as SED plume and polar cap patches. Our study focuses on ionosphere-thermosphere (IT) responses during the April 23, 2023 storm with the minimum Dst reaching -209 nT. We primarily use GITM (Global Ionosphere-Thermosphere Model) and SAMI3 (Another Model of the Ionosphere) to simulate the IT responses. In total, we performed three model runs: (a) GITM driven by empirical high-latitude drivers; (b) one-way coupled GITM-SAMI3 driven by empirical high-latitude drivers; (c) one-way coupled GITM-SAMI3 using the IE output from BASTRUS MHD model with the new COMPASS conductance model. We study the formation and evolution of SEDs by examining key parameters, such as TEC (total electron content), ion drifts and neutral winds. The TEC dataset used to validate the simulation results is the new VISTA (Video Imputation with SoftImpute, Temporal smoothing and Auxiliary data) dataset. Combining the different models and observations, we can better understand the generation and evolution processes of these ionospheric high-density features and predict relevant space weather impact.