High-Latitude Thermosphere and Ionosphere Density Response to the May 2024 Geomagnetic Storm Observed by LLITED CubeSat

On May 10th, 2024, active region AR3664 on the Sun produced several X-class flares and subsequently launched multiple halo CMEs earthward. This event was the first geomagnetic storm in 21 years to be classified as a G5 geomagnetic storm, the highest rating. The NASA Low-Latitude Ionosphere/Thermosphere Enhancements in Density (LLITED) CubeSat observed the high latitude neutral density and ion density at altitudes ~410-440 km providing unique high-resolution in-situ measurements of the coupled ionosphere-thermosphere response to the May 2024 storm. The geomagnetic activity enhanced Joule heating in the auroral regions influencing the thermosphere neutral gas and consequently coupled the ionosphere plasma. A few hours after the Dst-index reached a minimum on May 11th the thermosphere density was enhanced 305% on average over the Southern Hemisphere high-latitude LLITED B trajectory compared to May 7th quiet times. The plasma density observed co-locally was depleted by 58% compared to the quiet time density for latitudes poleward of -70 °MLAT. These results are compared to both TIE-GCM physics-based model and the NRLMSIS empirical model. While a geomagnetic event of this magnitude may occur once every few decades, this storm occurred in an era with an unprecedented number of spacecrafts in low earth orbit. The significant density enhancements of the thermosphere led to orbital decay for many satellites. Due to this hazard, it is increasingly important to understand the thermosphere/ionosphere response to geomagnetic storms.