Response of the Thermosphere‐Ionosphere System to an X‐Class Solar Flare: 30 March 2022 Case Study.

The response of the thermosphere ionosphere system to an X1.3 class solar flare is studied using observations of the total electron content (TEC) and the Global Ionosphere Thermosphere Model (GITM) simulations. The solar flare erupted from the active region AR12975 on 30 March 2022. Owing to the absence of accompanying severe geomagnetic activity, it was possible to isolate the effects of the flare on the upper atmosphere. TEC data are processed for Continental USA (CONUS), employing filtering and binning techniques to create 2D variation maps. The spectral content of the TEC variations is analyzed using a wavelet coherence method. The immediate response of the solar flare exhibited broad similarities, while notable differences were observed during the recovery period between the East and West sides of the CONUS. GITM is used to explore the East–West asymmetry of the key T‐I parameters. Simulation results reveal that the coinciding interplanetary magnetic field southward turning had a greater influence on these parameters compared to the solar flare, while their nonlinear interaction introduced complex variations. Additional investigation reveals gravity wave damping also contributes to the asymmetric solar flare response. Plain Language Summary: This study examines how a solar flare, which erupted on 30 March 2022, affected the Earth's upper atmosphere. We used satellite data to measure changes in the amount of charged particles in the atmosphere above the United States (specifically the area known as CONUS) and ran computer simulations to better understand these changes. We found that while the immediate reaction of the atmosphere to the flare was similar across the CONUS, differences emerged between the East and West during the recovery phase. The simulations showed that these differences were influenced by local time differences between the East and West, as well as by variations in the Earth's magnetic field geometry above these regions. Additionally, the study identified that the damping of gravity waves also played a role in these regional differences. Overall, the research highlights how complex interactions between various factors can lead to different responses to solar events in different parts of the CONUS. Key Points: Spectral content and temporal variation of total electron content perturbations associated with an X1.3 Solar Flare are analyzedThe thermosphere‐ionosphere exhibits a longitudinal flare response during the recovery phaseThe nonlinear interaction of the solar flare with the southward turning of the interplanetary magnetic field Bz ${\mathrm{B}}_{z}$ introduces significant variability [ABSTRACT FROM AUTHOR]