# Near-Real-Time Global Thermospheric Density Variations Unveiled by Starlink Ephemeris
## 3 Results
Notably, the number of special maneuvers during the period from 8-14 October significantly exceeded that during the quiet Dst period before 8 October. The additional spikes in Figure 4b on 8 and 11 October further corroborate the increased maneuver frequency during thermospheric disturbances. Therefore, the maneuver frequency of Starlink satellites can, to some extent, reflect the level of thermospheric disturbance. Next, we analyze the thermospheric information embedded in the Starlink ephemeris from the perspective of energy variations. Figure 5 presents the mechanical energy loss  
Figure 4: Maneuver statistics of Starlink satellites in Shell 1. (**a**) Number of maneuvering satellites per orbital plane in Shell 1, calculated with a 5-min time window. (**b**) Total number of maneuvering satellites across all orbital planes in Shell 1, calculated with a 5-min time window. (**c**) Dst index provided for reference. derived from Starlink ephemerides and Swarm-B thermospheric density data during 1-30 October 2024. During this period, Swarm-B maintained an altitude of approximately 512 km, with its ascending and descending nodes crossing the equator at LTs of \(\sim\)09:40 and \(\sim\)21:40, respectively. The thermospheric density data along the ascending orbit of Swarm-B, computed by ESA, are shown in Figure 5a, while the corresponding Dst index is plotted in Figure 5f for reference. Figure 5a reveals that the thermospheric density during quiet conditions was approximately \(3\times 10^{-12}\) kg/m\({}^{3}\). During the onset of the first storm (as the Dst index gradually declined), the thermospheric density exhibited an enhancement. In the recovery phase, the density not only recovered rapidly but also dropped below the pre-storm levels. This behavior aligns with the characteristic post-storm overcooling of the thermosphere, attributed to the prolonged recovery time of NO cooling relative to thermospheric temperature and density. As a result, NO cooling continues to operate even after a storm, further cooling the thermosphere [46]. This phenomenon was more pronounced during the subsequent strong storm. At 01:00 UT on 11 October, the Dst index reached its minimum of \(-333\) nT, marking the end of the main phase. While the Dst index recovered to quiet time levels, the thermospheric density remained significantly lower than the pre-storm values until 26 October, persisting for an extended duration. Figure 5: Variations of mechanical energy loss derived from Starlink satellites and Swarm-B. (**a**) Thermospheric density of Swarm-B (units: \(10^{-12}\) kg/m\({}^{3}\)). (**b**) Mechanical energy loss of Swarm-B. (**c**) Mechanical energy loss of STARLINK-44934. (**d**) Mechanical energy loss of STARLINK-46047. (**e**) Mechanical energy loss composed of multiple Starlink satellites whose orbital LTs are nearly 09:40. The Starlink satellite IDs used in each period are listed below the panel. (**f**) Dst index provided for reference. The mechanical energy loss of Swarm-B, computed from thermospheric density data using Equation (3), is presented in Figure 5b. A comparison with Figure 5a reveals that the variations in mechanical energy loss are nearly proportional to the thermospheric density, with discrepancies primarily attributable to the \(C_{d}A\) term, which varies with Swarm-B's attitude and thermospheric temperature. This proportional relationship between mechanical energy loss and thermospheric density should also hold for Starlink satellites. The mechanical energy loss derived from Starlink ephemerides is illustrated in Figure 5c,d. Here, we present continuous results for two Starlink satellites: STARLINK-44934 (Figure 5c) and STARLINK-46047 (Figure 5d). Unlike Swarm satellites, which are near-polar orbiters with slowly varying equator-crossing LTs, Starlink satellites, designed with an inclination of 53\({}^{\circ}\), exhibit rapid orbital LT variations.