Spikes that Make You Say “Yikes”

Martin G Connors1, Sébastien Guillon2, Mark J. Engebretson3, Xiangning Chu4, Kyle Wallace Reiter5, David H Boteler6, Christopher T Russell7, Brian J Jackel5 and Ian Schofield1, (1)Athabasca University, Athabasca, AB, Canada, (2)Hydro-Québec, Transénergie, Montréal, QC, Canada, (3)Augsburg University, Physics, Minneapolis, MN, United States, (4)University of California Los Angeles, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA, United States, (5)University of Calgary, Calgary, AB, Canada, (6)Natural Resources Canada, Ottawa, ON, Canada, (7)University of California Los Angeles, Department of Earth Planetary and Space Sciences, Los Angeles, CA, United States
Abstract:
Examination of times of voltage distortion events (a GIC proxy) in the Hydro-Québec power grid in northeastern North America suggests that most are associated with auroral currents on the nightside of Earth. Some fraction, during the daytime, is instead associated with changes in the solar wind, including but not restricted to compressional sources of sudden impulses (SI). In both cases, GIC activity seems to mainly be associated with spikes, mainly in the vertical component, of magnetic fields detected in the nearby AUTUMNX, MACCS, and CANMOS magnetic networks. These spikes can be very large, exceeding 1000 nT, and last of order only minutes, giving rise to large rates of change of the magnetic field. Consideration of Faraday’s Law suggests that the vertical component is the most geoeffective field component. Nightside magnetic spike signals associated with voltage distortion triggers in the Hydro-Québec grid tend to be large, leading us to refer to them as Large Impulsive Magnetic Events (LIME) in distinction to other magnetic impulse events (MIE). With emphasis on two large events, an SI and a LIME, we will discuss physical processes giving rise to such spikes, with reference to pre-existing models developed by Araki and Lanzerotti, respectively. In the case of SI, shock aurora is already well known. We present a case of LIME showing a clear association with an unusual and dynamic streamer aurora. The amplitude, spatial localization, and short duration of LIME events suggest that they are distinct from substorms, although they occur during magnetically active periods.
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