Ground Magnetic Perturbations due to Neutral-wind Driven Currents

Ground magnetic perturbations (dB) and geomagnetically induced currents (GICs), which are a manifestation of space weather impact at the ground level, pose a serious threat to the reliability of important infrastructures, such as powerlines and pipelines, especially during intense geomagnetic storms. Disturbances of the current system in the near-Earth environment due to a variety of drivers are the sources for dB and GICs. Previous studies on dB and GICs mostly rely on global MHD models, which explicitly calculate the magnetospheric currents and carry certain assumptions about the ionosphere currents. Therefore, the role of ionospheric and thermospheric processes has not been fully evaluated. In this study, Global Ionosphere Thermosphere Model (GITM) simulations for an idealized storm event have been conducted. Simply, the high-latitude electrodynamic forcing (potential pattern and particle precipitation) have been specified by empirical models. dB due to neutral-wind driven currents have been compared to dB caused by magnetospheric convection driven currents during both the main and recovery phases. Neutral-wind driven currents are found to contribute to ~10-20% of the total dB at locations where magnetospheric convection presents during the main phase. During the recovery phase when the ion-convection pattern retreats to high latitudes, neutral-wind driven currents can be the major sources for dB at middle latitudes on the dayside due to the flywheel effect and the large dayside conductance. Meanwhile, comparisons and coupling with a MHD model, such as Block-Adaptive-Tree Solar-Wind Roe-Type Upwind Scheme (BATSRUS) will be conducted in order to evaluate the significance of the neutral-wind dynamo to the whole magnetosphere-ionosphere-thermosphere (M-I-T) system and ground magnetic perturbations.