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Abstract:
High-resolution Thermospheric Neutral Density (TND) measurements from Low Earth Orbit (LEO), are valuable to accurately estimate the short-term atmosphere abrupt disturbances, triggered by magnetospheric forcing. For our study, the GRACE-FO satellites (Gravity Recovery and Climate Experiment Follow-On) 10s accelerometer-derived TND measurements were processed. We also derived the TND by determining the atmospheric drag force through centimeter-level reduced-dynamic Precise Orbit Determination (POD) using onboard Global Navigation Satellite System (GNSS) observations. We compare the resulting densities with those of the NRLMSIS-2.0 empirical atmosphere model to examine the status of solar cycle 25 between August 29 and December 31, 2020. Our investigations indicate that the POD-derived density shows a good agreement with accelerometer-derived density, which exhibited a more sensitive response to magnetic storms compared with NRLMSIS-2.0. The intensity of neutral densities enhancement in the Southern hemisphere surpasses that in the Northern one. The observed 4-month enhancing disturbances suggest a shift from relatively quiescent to a much more active phase of solar activity, revealing unexpected dependencies on the temporal and spatial characteristics. Furthermore, the Wygant coupling function was applied to model the response of the geomagnetic field changes in the solar wind, and quantify the impact of geomagnetic activities on the density of the upper atmosphere. All these findings hold the potential to improve our understanding of LEO orbital drag.
