Rapid geomagnetic variations during HSS/SIR, ICME sheath and magnetic
cloud-driven geomagnetic storms
Abstract
The most detrimental geomagnetically induced currents (GICs) documented
to date have all taken place during geomagnetic storms. Yet, the
probability of GICs throughout geomagnetic storms driven by different
solar wind transients, such as high-speed streams/stream interaction
regions (HSS/SIR) or interplanetary coronal mass ejection (ICME) sheaths
and magnetic clouds (MC), is poorly understood. We present an algorithm
to detect geomagnetic storms and storm phases, resulting in a catalog of
755 geomagnetic storms from January 1996 to June 2023 with the solar
wind drivers. Using these storms and the IMAGE magnetometer network, we
study the temporal and spatial evolution of spikes in the external
dH\textsubscript{ext}/dt greater than 0.5 nT/s during
geomagnetic storms driven by HSS/SIR, sheaths and MCs. Spikes occur more
often toward the end of the storm main phase for HSS/SIR and MC-driven
storms, while sheaths have spikes throughout the entire main phase.
During the main phase most spikes occur in the morning sector around 05
magnetic local time (MLT) and the extent in MLT is narrowest for MCs and
widest for sheaths. However, spikes in the pre-midnight sector during
the main and recovery phases are most prominent for HSS/SIR-driven
storms. During the storm sudden commencement (SSC), three MLT hotspots
exist, the post-midnight at 04 MLT, pre-noon at 09 MLT and afternoon at
15 MLT. The pre-noon hotspot has the highest probability of spikes and
the widest extent in magnetic latitude.