The total energy transfer from the solar wind to the magnetosphere is governed by the reconnection rate at the magnetosphere edges as the IMF $B_z$ turns southward. The delayed response of the ring current to solar wind driving can account for the anomalous growth of the SYM-H under northward IMF $B_z$. The geomagnetic storm on 21-22 January 2005 is considered to be anomalous as the SYM-H index that signifies the strength of ring current, grows and has a sustained peak value lasting more than 6 hrs under northward IMF $B_z$ conditions. In this work, first the standard WINDMI model is utilized to estimate the growth and decay of various magnetospheric currents by using several solar wind-magnetopsehre coupling functions. However, it is found that the WINDMI model driven by any of these coupling functions is not fully able to explain the enhancement of SYM-H under northward IMF $B_z$. The SYM-H variations during the entire duration of the storm were only reproduced when the effects of the dense plasma sheet were included in the WINDMI model. The limitations of directly-driven models relying purely on the solar wind parameters and not accounting for the state of the magnetosphere are highlighted by this work.

In this study, we present ionospheric observations of field-aligned currents from AMPERE and the ESA Swarm A satellite, in conjunction with high-resolution thermospheric density measurements from accelerometers on board Swarm C and GRACE-FO, for the 3rd and 4th February 2022 geomagnetic storms that led to the loss of 38 Starlink internet satellites. We study the global storm time response of the thermospheric density enhancements, including their growth, decay, and latitudinal distribution. We find that the thermospheric density enhances globally in response to high-latitude energy input from the magnetosphere-solar wind system, and takes at least a full day to recover to pre-storm density levels. We also find that the greatest density perturbations occur at polar latitudes consistent with the magnetosphere-ionosphere dayside cusp, and that there appeared to be a saturation of the thermospheric density during the geomagnetic storm on the 4th. Our results highlight the critical importance of high-latitude ionospheric observations when diagnosing potentially hazardous conditions for low-Earth-orbit satellites.