He told Express.co.uk: “The high latitudes are the most vulnerable, it’s happened in Canada in 1989 when the power went down in Quebec.”
This geomagnetic storm caused a nine-hour outage of Hydro-Quebec's electricity transmission system.
As it happened during the Cold War it also left many terrified that a nuclear strike might be in progress.
Others incorrectly considered the intense auroras to be associated with the Space Shuttle mission STS-29.
Geomagnetic storms are caused by CME’s which produce "large expulsions of plasma and magnetic field from the Sun’s corona," according to the National Oceanic and Atmospheric Administration (NOAA).
Source : https://www.express.co.uk/news/science/1505137/solar-storm-warning-experts-worried-global-power-outage-last-weeks-space-weather209