Speaker
Description
During the first G3 storm of Solar Cycle 25, the passage of a solar filament on 12 May 2021 produced a strong geomagnetic storm and a rich response in Earth's magnetosphere-ionosphere-telluric-technology system. We use data from the North American Electric Reliability Corporation (NERC) to investigate the effects of the event on the power grid along the US East Coast and compare the timing and magnitude to other locations around the globe. We find geomagnetically induced currents (GICs) in the mid-latitude eastern US power grid and significant penetrating electric fields (PEFs) in the same longitude sector. The disturbance responses were 2-30 A GICs measure in grid monitors with coincident perturbations in ground magnetometer arrays and geomagnetic indices, and unusually robust variations in total electron content in the American sector and beyond. The storm was pre-condition by early SW density enhancements in the first portion of the solar filament. The largest GICs and delta-TEC occurred with a solar wind (SW) +/- pressure pulse, effects of which were observed globally at 1200-1220 UT in ground- and space-based systems. The negative pressure pulse appeared in the GIC record from the central US to Europe, showing that impulsive SW density variations can be especially impactful to engineered systems. Long duration GIC effects followed from 1230-1530 UT producing a sustained level of moderate perturbations and potentially dangerous response at a few locations. We discuss specific drivers in the solar wind and magnetosphere and their relation to the power grid and GNSS signals. We emphasize the value of the NERC GIC data base for Operations to Research and vice versa and the utility of combining these data with other sources.
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