Mesosphere and Lower Thermosphere (MLT) Density Responses to the May 2024 Superstorm at Mid-to-High Latitudes in the Northern Hemisphere Based on Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER) Observations

Abstract

The thermospheric density response during geomagnetic storms has been extensively explored, but with limited studies on the density response in the Mesosphere and Lower Thermosphere (MLT) region. In this study, the density response in the MLT region at mid-to-high latitudes of the Northern Hemisphere during the intense geomagnetic storm in May 2024 is investigated using density data from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument aboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. The results indicate that during the geomagnetic storm, the density response exhibits both significant decreases and increases; specifically, approximately 25.2% of the observation points show a notable reduction within a single day, with the maximum decrease exceeding −59.9% at 105 km. In contrast, around 16.5% of the observation points experience a significant increase over the same period, with the maximum increase surpassing 82.4% at 105 km. The distribution of density changes varies with altitudes. The magnitude of density increases diminishes with decreasing altitude, whereas the density decreases exhibit altitude-dependent intensity variations. Density decreases are primarily concentrated in high-latitude regions, especially in the polar cap, while density increases are mainly observed between 50°N and 70°N. The intensity of density response is generally stronger in the dusk sector than in the dawn sector. These results suggest that atmospheric expansion and uplift driven by temperature variations are the primary factors underlying the observed density change.

Keywords

• SABER
• the mesosphere and lower thermosphere
• geomagnetic storm
• neutral density