FG: Understanding the causes of geomagnetic disturbances in geospace for hazard analysis on geomagnetically induced currents

Focus Group Chairs

Xueling Shi, Virginia Tech (xueling7@vt.edu)

Dogacan Su Ozturk, University of Alaska Fairbanks (dsozturk@alaska.edu)

Mark Engebretson, Augsburg University (engebret@augsburg.edu)

Zhonghua Xu, Virginia Tech (zxu77@vt.edu)

Erin Joshua Rigler, USGS (erigler@usgs.gov)

Overview

Geomagnetic disturbances (GMDs) related to various phenomena in the near-Earth space environment can induce geoelectric fields within the electrically conducting Earth. In turn these geoelectric fields drive electric currents that can flow through technological infrastructure in the form of geomagnetically induced currents (GICs) and cause potential damage to power grid, pipelines, and submarine cables. Our focus group (FG) aims to improve the physical understanding of the causes of GMDs through observations, numerical simulations, and machine learning techniques in the solar wind-magnetosphere-ionosphere-ground coupled system for hazard analysis on GICs. Understanding the causes of GMDs is crucial in the development and validation of models which aim to accurately and reliably predict the variations of geoelectric fields and GICs and are objectives of the National Space Weather Strategy and Action Plan (NSWSAP, 2019).

Topic Description

Geomagnetic disturbances (GMDs) have long been used to derive global geomagnetic activity indices (e.g., Kp, AE, and Dst), remote sense the magnetosphere-ionosphere (M-I) currents and plasma waves, and as inputs to geoelectric field/GIC models. The sources of GMDs are directly related to various M-I currents and plasma waves which can be attributed to various drivers in the solar wind-magnetosphere-ionosphere-ground coupled system. Despite extensive research, questions still remain regarding the common sources and driving mechanisms of GMDs. Many studies have focused on the association of GMDs with large-scale geomagnetic activity including storms and substorms. Several more recent statistical studies have analyzed the association of nighttime GMDs with global inputs (IMF and solar wind) and geomagnetic indices (e.g., Engebretson et al., 2021a, 2021b), and case studies have focused on more local phenomena such as overhead ionospheric currents and auroras (Belakhovsky et al., 2019, Dimmock et al., 2019, Apatenkov et al., 2020; and Weygand et al., 2021). The M-I currents that drive nighttime GMDs appear to be linked to mesoscale disturbances in the magnetotail, and their association with substorms and/or intervals of negative IMF Bz suggest the influence of magnetotail reconnection. Up to now, however, there have been very few reports connecting nighttime GMD events to specific disturbances in the magnetotail.

In addition, direct geoelectric field measurements are very limited and GIC measurements are usually not publicly available, many studies rely on dB/dt or ∆B as a proxy. However, it is still not yet well understood whether dB/dt or ∆B is a good proxy of GICs or under what conditions GMDs will couple to extreme geoelectric fields and GICs. Therefore, an interdisciplinary community-wide effort involving the space science data analysis, space weather modelling, magnetotelluric (MT), and the power system engineering communities, is needed to advance our understanding of the causes of GMDs and hazardous GICs. We propose an FG to address the following questions:

Q1: What are the drivers of the formation and evolution of space weather significant GMDs?

Q2: To what extent can different models predict GMDs and what are immediate missing components to improve GMD prediction?

Q3: What is the most important input the GEM community could provide to those who study geoelectric fields and GICs?