Characteristics of extreme geoelectric fields and their possible causes: Localized peak enhancements

Abstract

One of the major challenges pertaining to extreme geomagnetic storms is to understand the basic processes associated with the development of dynamic magnetosphere‐ionosphere currents, which generate large induced surface geoelectric fields. Previous studies point out the existence of localized peak geoelectric field enhancements during extreme storms. We examined induced global geoelectric fields derived from ground‐based magnetometer recordings for 12 extreme geomagnetic storms between the years 1982 and 2005. For the present study two important extreme storms, 29 October 2003 and 13 March 1989, are shown. The primary purpose of this paper is to provide further evidence on the existence of localized peak geoelectric field enhancements and to show that the structure of the geoelectric field during these localized extremes at single sites can differ greatly from globally and regionally averaged fields. Although the physical processes that govern the development of these localized extremes are still not clear, we discuss some possible causes.

A Study of Intense Local dB/dt Variations During Two Geomagnetic Storms

“…Enriching our knowledge of the development of dynamic M‐I currents during major geomagnetic storms is one of the top priorities in the space weather community today. For GIC studies, it is critical that we understand the complex processes, both external and internal, that regulate currents in the near‐Earth space environment (e.g., Adebesin et al, ; Ngwira et al, , and references therein).…”

“…Several studies show that during geomagnetic disturbances, storm‐enhanced high‐latitude peak geomagnetic perturbations that cause large GICs tend to be localized (e.g., Boteler & Jansen van Beek, ; Pulkkinen et al, , ; Ngwira et al, , and references therein). The geomagnetic structures associated with localized extremes at single sites can be greatly different from structures associated with globally or regionally averaged fields (Ngwira et al, ; Pulkkinen et al, ). Extreme d B /d t variations can significantly impact GICs locally, but the impact on power system stability as a whole is not well understood.…”

Improving the modeling of geomagnetically induced currents in Spain

“…The combination of all the above mentioned factors in a worst case scenario can make the storm time geoelectric induction reach hazardous levels at a local scale. Regarding the hazard assessment, upper limits for the potentially biggest geomagnetic storm or estimates of return periods of a hypothetical extreme event are thus of great value, which causes studies on probability of extreme values to proliferate [e.g., Thomson et al ., ; Pulkkinen et al ., ; Love , ; Ngwira et al ., ; Nikitina et al ., ; Wintoft et al ., ; Riley and Love , ].…”

Space Weather Quarterly Volume 13, Issue 1, 2016

“…Another example of future challenges pertains to recent discovery of the role small spatial-scale (~100 km) ionospheric features play in generating extreme geoelectric fi elds [Pulkkinen et al, 2015a;Ngwira et al, 2015]. While small spatial-scale ionospheric features appear to play a signifi cant role in driving extreme geoelectric fi elds, it is not yet clear what solar wind-magnetosphereionosphere processes are responsible for these features.…”