Investigation of Pc5 pulsations and their correlation with solar wind parameters during intense geomagnetic storms

This study examines Pc5 ultra-low frequency (ULF) waves and their relationship with solar wind parameters and geomagnetic indices during two extended periods of intense ULF activity on 19 February 2014 and 22–23 June 2015. We analyze observations from ground-based magnetometers and the Operating Missions as Nodes on the Internet (OMNI) dataset, employing continuous wavelet transform (CWT) and cross-correlation as primary statistical tools. Our results reveal that: (1) interplanetary parameters and geomagnetic indices exhibit strong correlations with Pc5 pulsations; (2) the majority of significant Pc5 power is concentrated within the 6–9 min period band. This suggests that low-latitude geomagnetic fluctuations are not locally generated but rather reflect global geomagnetic field variations originating in the magnetosphere and high-latitude ionosphere, consistent with previous findings. While the southward component of the Interplanetary Magnetic Field (IMF) $B_z$ is often considered the primary driver of geomagnetic storms, we find its influence on Pc5 pulsations to be minimal. Instead, our analysis shows that ground-based Pc5 power scales with solar wind speed, corroborating the role of solar wind dynamics in modulating Pc5 wave activity. These findings enhance our understanding of Pc5 wave excitation mechanisms and their dependence on solar wind conditions during geomagnetic storms.