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

• Published in: Space Weather Vol. 21; no. 11
• Main Authors: Zhang, T., Ebihara, Y., Tanaka, T.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 01.11.2023
• Subjects: Amplitudes; Dynamic pressure; Electric currents; Electric fields; Geoelectric fields; Geoelectricity; geomagnetic disturbance; Geomagnetic variations; geomagnetically induced current; Geomagnetism; Impulse response; Ionosphere; Ionospheric currents; Ionospheric propagation; Latitude; Magnetic disturbances; Magnetohydrodynamic simulation; Magnetospheres; MHD simulation; Night; Perturbation; Polar environments; Polar regions; Québec blackout; Saturn; Simulation; Solar wind; sudden commencement; Vortices
• ISSN: 1542-7390; 1539-4964; 1542-7390
• DOI: 10.1029/2023SW003493

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. Plain Language Summary The sudden commencement (SC) is an impulse response of the magnetosphere‐ionosphere system caused by a sudden change in dynamic pressure of the solar wind. However, the generation of SC‐associated magnetic disturbances on the ground are not well understood, especially those from the impulse‐associated field‐aligned currents. We performed magnetohydrodynamic simulations to investigate the responses of ionospheric currents, which cause these geomagnetic variations, to the sudden change in solar wind dynamic pressure. The simulation results show that the large‐amplitude ionospheric current of the twin vortex type appears on the dayside, and propagates to the nightside at high latitudes. The ionospheric current causes the large‐amplitude magnetic disturbances not only on the dayside, but also on the nightside. We also calculated the electric field induced by the magnetic disturbances on the ground. From the comparison between the simulation and the observation, we suggest that the Québec blackout could be caused by the ionospheric current of the vortex type propagating from the dayside to the nightside, triggered by a large jump of the solar wind dynamic pressure. Key Points We investigated the ground magnetic disturbances in response to jumps in solar wind dynamic pressure using magnetohydrodynamic simulations For large jumps, the ionospheric current related to the main impulse (MI) causes significant magnetic disturbances on the nightside MI‐associated Hall currents can explain the large geomagnetic disturbances in Canada when the Québec blackout occurred on 13 March 1989