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Geomagnetically Induced Currents at Middle Latitudes: 1. Quiet-time Variability
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  • Adam C Kellerman,
  • Ryan Michael McGranaghan,
  • Jacob Bortnik,
  • Brett Anthony Carter,
  • Joseph Hughes,
  • Robert Arritt,
  • Karthik Venkataramani,
  • Charles H Perry,
  • Jackson C McCormick,
  • Chigomezyo M Ngwira,
  • Morris B. Cohen,
  • Jia Yue
Adam C Kellerman
University of California Los Angeles, University of California Los Angeles

Corresponding Author:[email protected]

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Ryan Michael McGranaghan
Atmosphere and Space Technology Research Associates, Atmosphere and Space Technology Research Associates
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Jacob Bortnik
University of California Los Angeles, University of California Los Angeles
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Brett Anthony Carter
RMIT University, RMIT University
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Joseph Hughes
Atmosphere and Space Technology Research Associates, Atmosphere and Space Technology Research Associates
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Robert Arritt
EPRI, EPRI
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Karthik Venkataramani
Atmospheric and Space Technology Research Associates, Atmospheric and Space Technology Research Associates
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Charles H Perry
EPRI, EPRI
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Jackson C McCormick
Georgia Institute of Technology, Georgia Institute of Technology
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Chigomezyo M Ngwira
Atmospheric and Space Technology Research Associates, Atmospheric and Space Technology Research Associates
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Morris B. Cohen
Georgia Institute of Technology, Georgia Institute of Technology
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Jia Yue
Goddard Space Flight Center, Goddard Space Flight Center
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Abstract

Geomagnetically induced current (GIC)s at middle latitudes have received increased attention after reported power-grid disruptions due to geomagnetic disturbances. However, quantifying the risk to the electric power grid at middle latitudes is difficult without understanding how the GIC sensors respond to geomagnetic activity on a daily basis. Therefore, in this study the question “Do measured GICs have distinguishable and quantifiable long- and short-period characteristics?’ is addressed. The study focuses on the long-term variability of measured GIC, and establishes the extent to which the variability relates to quiet-time geomagnetic activity. GIC quiet-day curves (QDC)s are computed from measured data for each GIC node, covering all four seasons, and then compared with the seasonal variability of Thermosphere-Ionosphere- Electrodynamics General Circulation Model (TIE-GCM)-simulated neutral wind and height-integrated current density. The results show strong evidence that the middle-latitude nodes routinely respond to the tidal-driven Sq variation, with a node-specific dependence upon the direction of the ionospheric currents. The strong dependence of the GIC on the Sq currents demonstrates that the GIC QDCs may be employed as a robust baseline from which to quantify the significance of GICs during geomagnetically active times and to isolate those variations to study independently. The QDC-based significance score computed in this study provides power utilities with a node-specific measure of the geomagnetic significance of a given GIC observation. Finally, this study shows that the power grid acts a giant sensor which is sensitive to ionospheric current systems, even at middle latitudes.
Feb 2022Published in Space Weather volume 20 issue 2. 10.1029/2021SW002729