Impact of Increasing Greenhouse Gases on the Ionosphere and Thermosphere Response to a May 2024-Like Geomagnetic Superstorm

The Community Earth System Model (CESM) Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCM-X) is used to investigate how the ionosphere-thermosphere response to a May 2024-like geomagnetic storm changes with increasing greenhouse gases. Coupled CESM(WACCM-X) simulations are first performed following the Coupled Model Intercomparison Project Phase 6 Shared Socioeconomic Pathway 5–8.5 from 2000 to 2090. The May 2024 geomagnetic superstorm is then simulated in 2016, 2040, 2061, and 2084, corresponding to surface (Formula presented.) levels of 403, 500, 652, and 918 ppmv, respectively. The CESM(WACCM-X) simulations indicate that increasing levels of (Formula presented.) weakens the absolute neutral density response at 350 km. However, the relative response is increased with increasing levels of (Formula presented.), which is partly due to the decrease in the background neutral density. Due to a weaker response in thermosphere composition and meridional neutral winds, the ionospheric response in absolute terms also weakens with increasing levels of (Formula presented.).