Global thermospheric density response to the May 2024 extreme storm: TianMu-1 constellation observations

This study analyzes the May 2024 geomagnetic storm's impact on thermospheric mass density using TianMu-1 constellation satellites (TM02, TM06, TM07, TM11, TM15). Observations reveal intense large-scale Traveling Atmospheric Disturbances (TADs) originating at high latitudes and propagating equatorward. TM02 observations captured the evolution of a TADs structure: initial amplitude ~3.89×10–12 kg/m3 at hundreds of kilometers scale, subsequently intensifying to 4.78×10–12 kg/m3 with spatial extent expanding to thousand-kilometer level. Significant hemispheric asymmetry was observed: absolute density was predominantly higher in the northern hemisphere (TM02, TM06, TM07, TM11), while relative density difference consistently showed greater enhancements in the southern hemisphere across all satellites, with maximum north-south density differences exceeding 195%–640% above 60° latitude. In conjunction with SuperDARN observations, this striking hemispheric asymmetry is likely attributed to disparities in plasma convection patterns between the two hemispheres. Furthermore, density perturbation characteristics exhibited strong local time dependence: near noon (~10.7 LT, TM02 descending), northern hemisphere onset preceded the southern onset. Conversely, near dusk (~17.6 LT, TM15 descending), southern onset led the northern onset by approximately 3 hours. Ascending orbits (TM02, TM06, TM07, TM15) typically yielded larger, global density enhancements compared to smaller, southern-confined enhancements during descending orbits. TM11 showed comparable perturbations in both ascending and descending orbit. Leveraging its unique orbital architecture, the TianMu-1 constellation enables global near-simultaneous multi-local time sampling, providing robust data foundation for both scientific research and engineering applications.