Storm-Time Neutral Density Perturbations at Multiple Temporal- and Spatial-Scales: Data-Model Comparisons

Multi-scale neutral density perturbations have important implications for the coupled ionosphere-thermosphere (I-T) system and its dynamics, especially during geomagnetic storms. However, the characteristics of the density perturbations on different spatial and temporal scales have not been investigated thoroughly so far. In this work, we present a detailed model-data comparative study of the storm-time density perturbations at different scales based on Gravity Recovery and Climate Experiment (GRACE) -A and -B satellite data and numerical simulations from the global ionosphere-thermosphere model (GITM). The GITM simulations are driven by the time-dependent field-aligned currents (FACs) from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) along with the AMIE auroral electron precipitation patterns. The NCAR ionospheric electrodynamo model was utilized to obtain the high-latitude electric potential and the global neutral dynamo, which allows GITM to simulate the storm-time neutral density perturbations during the moderate 2016 Jan - Feb storm as well as the intense 2015 St. Patrick Day storm. The GRACE satellite observations show that the neutral density perturbations at specific spatial (~250 km) and temporal (34 s) scales depend on latitude and the storm phases. In general, the GITM simulations reproduce the most salient spatial and temporal density perturbations very well, but the mesoscale structures are underrepresented. Moreover, in order to extract multi-scale neutral density perturbations from multiple spacecraft observations, we fly a series of virtual satellites with different temporal and spatial separations in our simulations. Our results provide important insights into multi-scale density perturbation characteristics in the upper thermosphere, which is particularly helpful to the refinement of NASA Geospace Dynamics Constellation (GDC) configuration.