In March of 1989, a highly active sunspot region released multiple extreme solar flares, including an X4.5 flare on March 10 and a M7.3 flare on March 12.
Solar flares are ranked as B, C, M, and X class, with B being the weakest and X the strongest. Within B, C, and M classes, flare strength is further ranked from 1 to 9. X class flares are the strongest, and the class is open-ended – i.e., X-class flares can go higher than 9. These strong flares of 1989 launched massive coronal mass ejections (CMEs) at Earth, hitting the planet on March 13.
The resulting disturbance was so large that aurorae were seen as far south as Texas and Cuba. In Quebec, where nonconductive bedrock couldn’t absorb the geomagnetically induced currents of the storm, the currents were forced into the Hydro-Quebec power grid. The province went dark, leaving 6 million people without power for nine to 12 hours. Operational glitches in power grids and communications systems were seen across the U.S. and Europe, as well, though none was as severe as the effects felt by Quebec. The event forced a paradigm shift in infrastructure preparation for geomagnetic storms. As a result, when multiple X-class flares hit Earth in the solar storm of May 2024, there was little effect on power grids.
