Statistical Modeling and Prediction of Ionospheric Equivalent Currents Based on SuperMAG Data

Abstract

We present a Solar Wind driven SuperMAG statistical Equivalent Current model (SW-SMEC), which represents the ionospheric equivalent currents in the Northern Hemisphere. The model is based on average current patterns derived from SuperMAG ground magnetometer data covering the solar cycle 23 (1997–2008). It predicts equivalent currents as function of the interplanetary magnetic field (IMF) clock angle, the solar wind electric field magnitude, and the Earth's dipole tilt. The equivalent currents predicted by our model show the well-known characteristics, such as strong dependence on the IMF north-south $\left(B_z\right)$ component and solar wind electric field. Positive IMF dawn-dusk $\left(B_y^{+}\right)$ component causes stronger equivalent currents than negative $\left(B_y^{-}\right)$ component. Equivalent currents are also stronger during summer than winter. The SW-SMEC model was tested in two case studies of geomagnetic storms, driven by a high-speed stream (HSS) and an interplanetary coronal mass ejection (ICME), respectively. The model succeeds in reproducing the main features of both HSS- and ICME-driven storms with comparable accuracy, as estimated by comparison with gridded SuperMAG data product. The accuracy is highest during the storm's main phase and lowest during the initial phase. A statistical study using 227 storms during the solar cycle 24 (2009–2019) shows that the model is more accurate with ICME-driven storms than with HSS-driven storms. It also shows that the optimal solar wind integration time for the model is typically 100 min, although it varies depending on the storm phase or driver.