Nighttime Geomagnetic Response to Jumps of Solar Wind Dynamic Pressure: A Possible Cause of Québec Blackout in March 1989

<jats:title>Abstract</jats:title><jats:p>By performing a global magnetohydrodynamic (MHD) simulation, we investigated magnetic disturbances on the ground at high‐latitudes in response to jumps in the solar wind dynamic pressure, namely a sudden commencement (SC). After the arrival of the jump, a pair of field‐aligned currents (FACs), related to the preliminary impulse, develop and travel in the anti‐sunward direction. Soon after another pair related to the main impulse (MI) appears and travels in the anti‐sunward direction. The horizontal ionospheric current associated with the MI remains strong when propagating to the nightside. On the dawnside the MI current flows sunward (anti‐sunward) resulting in northward (southward) ground magnetic disturbance at higher (lower) latitude in the post‐midnight sector. These features are similar to those observed in Canada in the high‐latitude post‐midnight sector when the Québec blackout took place on 13 March 1989. The nighttime geomagnetic perturbations associated with the MI occur regardless of the magnitude of the solar wind dynamic pressure and IMF orientation. The amplitude of the geoelectric field, which is closely related to the geomagnetically induced currents (GICs), reaches the maximum value just before and around the maximum of the southward magnetic disturbance. This is consistent with the moment at which the blackout occurred during the southward magnetic perturbation. We suggest that the blackout in Québec could be caused by the MI‐associated Hall current passing over the Hydro‐Québec power system on the nightside. The nighttime polar region is shown to be sensitive to hazardous GICs for large‐amplitude jumps in the solar wind dynamic pressure.</jats:p>