Influence of Solar Wind Parameters on the Geomagnetic Storm Occurrence and Intensity

Abstract

Understanding the complex interplay between solar wind parameters and geomagnetic storm dynamics remains a major challenge in space weather research. Our strategy applies a more comprehensive statistical analysis of the occurrence and intensity of geomagnetic storms than earlier studies. It examines both the individual and combined effects of solar wind velocity and density (V_sw, N_sw), as well as the southward component of the interplanetary magnetic field (IMF). We analyzed solar wind parameters such as V_sw and N_sw together with variable IMF parameters and storm-time D_st index values during Solar Cycles 24 and 25 (2008–2023). Our dataset includes all intense geomagnetic storms (D_st < –99 nT). For each event, we considered the solar wind and IMF conditions during the 3 days before and after the peak D_st value. Regression and correlation analyses showed that a sustained southward orientation of the IMF B_z component can trigger an intense geomagnetic storm even when the total IMF magnitude B_t remains relatively low. During the declining phase of Solar Cycle 24, the number of geomagnetic storms exceeded that observed during the cycle’s maximum phase, indicating that geomagnetic storm frequency does not always increase at solar maximum. During the minimum phase of Solar Cycle 24, no intense storms occurred despite high V_sw values. This finding indicates that elevated V_sw values do not necessarily produce intense geomagnetic storms. In addition, case studies of the April 24, 2023, and June 23, 2015, storms demonstrated that higher V_sw values do not always correspond to more intense storms, as compared with the event on March 17, 2015. These results suggest that numerous combinations of solar wind parameter behavior (N_sw, V_sw) and the IMF B_z component contribute to the potential intensity of geomagnetic storms. Furthermore, intervals of high V_sw values combined with a southward IMF B_z orientation can produce substantial magnetospheric disturbances that lead to intense geomagnetic storms. The obtained results emphasize the need to investigate multiple solar wind parameters in order to understand the drivers underlying geomagnetic storm activity.