Determining ULF Wave Contributions to Geomagnetically Induced Currents: The Important Role of Sampling Rate

Past studies found that large-amplitude geomagnetically induced current (GIC) related to magnetospheric Ultra Low Frequency (ULF) waves tend to be associated with periods >120 s at magnetic latitudes >60 degrees, with comparatively (a) smaller GIC amplitudes at lower latitudes and shorter wave periods and (b) fewer reports of waves associated with GIC at lower latitudes. ULF wave periods generally decrease with decreasing latitude; thus, we examine whether these trends might be due, in part, to the undersampling of ULF wave fields in commonly available measurements with 60 s sampling intervals. We use geomagnetic field (B), geoelectric field (E), and GIC measurements with 0.5-10 s sampling intervals during the 29-31 October 2003 geomagnetic storm to show that waves with periods

Automated summary

Previous studies have shown that large-amplitude geomagnetically induced current (GIC) related to magnetospheric Ultra Low Frequency (ULF) waves are more common at latitudes above 60 degrees and with periods longer than 120 seconds. Conversely, GIC amplitudes are smaller at lower latitudes and with shorter wave periods, and there are fewer reports of waves associated with GIC at lower latitudes. This study aims to investigate whether these trends are due to the undersampling of ULF waves in commonly available measurements with 60-second sampling intervals. Data from the 29-31 October 2003 geomagnetic storm, with sampling intervals of 0.5-10 seconds, is used to examine waves with periods...