Investigation of Pc5 pulsations effects and magnetospheric processes
during intense geomagnetic storms
Abstract
Giant pulsations belonging to the Pc5 frequency band were conceived by
Rolf (1931). Such pulsations are influenced by magnetospheric processes
produced by the solar wind. The purpose of this study is to investigate
the Pc5 ULF waves and their relationship to solar parameters and
geomagnetic indices, respectively, utilizing data from ground-based
magnetometers and data provided by Operating Mission as Nodes on the
Internet (OMNI). Magnetic observatories over Earth’s surface reported
intense long-period ULF activity on 19 28 February 2014 and 22-23 June
2015. We discovered a highly significant correlation between global Pc5
ULF waves and other interplanetary parameters, as well as a clear
peak-to-peak correspondence during storms. We performed continuous
wavelet transform (CWT) on the Pc5 integrated power (Ipow) and
discovered that the majority of the intense Pc5 spectra are localized
within the 64-256 minute Fourier period band. Our results suggest that
geomagnetic fluctuations observed at low latitudes do not originate
locally but rather are a reflection of global geomagnetic field
variations with primary sources in the magnetosphere and high latitude
ionosphere, which is consistent with the study of Gupta (1976). We
discovered only nominal effects of IMF Bz on Pc5 pulsations, despite its
southern counterpart being widely believed to be the principal driver of
geomagnetic storms. Additionally, we discovered a moderate effect of
solar wind pressure on Pc5 pulsations. A cross-correlation study, on the
other hand, indicated a strong and positive association between Pc5
pulsations and solar wind velocity without lag for both geomagnetic
activities.