Geomagnetically Induced Currents at Middle Latitudes: Quiet-time Climatology, Significance during Geomagnetic Disturbances, and Machine-Learning Modeling

Abstract:

A critical concern for owners and operators of the electric power grid is whether their systems are susceptible, and to what extent, to impacts from geomagnetic disturbances. In order to adequately monitor this risk, they need to integrate and accurately associate the data available to them. Key among the available data, but rarely available outside of power utilities, are Geomagnetically Induced Current (GIC) monitors that are designed to track with space weather and offer the most direct connection between the expected observed current for the prevailing geomagnetic conditions. In a set of studies conducted as part of the National Science Foundation Convergence Hub for the Exploration of Space Science (CHESS; https://www.chessscience.com/), over 12 months of measurements from multiple GIC nodes (available uniquely due to partnership with the EPRI Sunburst Program) at middle latitudes are analyzed to (a) quantify the quiet-time variability of the measured current, (b) quantify the significance of measured current during geomagnetically disturbed times, and (c) develop a machine-learning nowcast and forecast model of GIC for these specific locations at middle latitudes.

The quiet-time variability of the measured current flowing into transformers is shown to follow the diurnal variation associated with the Sq-current system at mid latitudes. The results are compared with TIEGCM simulations, and a quiet-day curve (QDC) is computed for each GIC node. The significance of any observed current is then defined with respect to the Sq-driven baseline, effectively improving the signal-to-noise ratio of each space-weather monitor. The efficacy of multiple ML models to nowcast and forecast these critical data are explored.