Geomagnetically induced currents caused by interplanetary shocks with different impact angles and speeds

Oliveira, D, Arel, D, Raeder, J, Zesta, E, Ngwira, C, Carter, B, Yizengaw, E, Halford, A, Tsurutani, B and Gjerloev, J 2018, 'Geomagnetically induced currents caused by interplanetary shocks with different impact angles and speeds', Space Weather, vol. 16, no. 6, pp. 636-647.

Document type: Journal Article
Collection: Journal Articles

Title Geomagnetically induced currents caused by interplanetary shocks with different impact angles and speeds
Author(s) Oliveira, D
Arel, D
Raeder, J
Zesta, E
Ngwira, C
Carter, B
Yizengaw, E
Halford, A
Tsurutani, B
Gjerloev, J
Year 2018
Journal name Space Weather
Volume number 16
Issue number 6
Start page 636
End page 647
Total pages 12
Publisher Wiley-Blackwell Publishing, Inc.
Abstract The occurrence of geomagnetically induced currents (GICs) poses serious threats to modern technological infrastructure. Large GICs result from sharp variations of the geomagnetic field (dB/dt) caused by changes of large-scale magnetospheric and ionospheric currents. Intense dB/dt perturbations are known to occur often in high-latitude regions as a result of storm time substorms. Magnetospheric compressions usually caused by interplanetary shocks increase the magnetopause current leading to dB/dt perturbations more evident in midlatitude to low-latitude regions, while they increase the equatorial electrojet current leading to dB/dt perturbations in dayside equatorial regions. We investigate the effects of shock impact angles and speeds on the subsequent dB/dt perturbations with a database of 547 shocks observed at the L1 point. By adopting the threshold of dB/dt = 100 nT/min, identified as a risk factor to power systems, we find that dB/dt generally surpasses this threshold when following impacts of high-speed and nearly frontal shocks in dayside high-latitude locations. The same trend occurs at lower latitudes and for all nightside events but with fewer high-risk events. Particularly, we found nine events in equatorial locations with dB/dt > 100 nT/min. All events were caused by high-speed and nearly frontal shock impacts and were observed by stations located around noon local time. These high-risk perturbations were caused by sudden strong and symmetric magnetospheric compressions, more effectively intensifying the equatorial electrojet current, leading to sharp dB/dt perturbations. We suggest that these results may provide insights for GIC forecasting aiming at preventing degradation of power systems due to GICs.
Subject Space and Solar Physics
Mesospheric, Ionospheric and Magnetospheric Physics
DOI - identifier 10.1029/2018SW001880
Copyright notice © 2018. American Geophysical Union. All rights reserved.
ISSN 1542-7390
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