Also known as the “Solar storm of 1859.” This was the most powerful solar flare ever observed, with the added bonus that it was directed at Earth. The consequences of the event were pretty spectacular at the time; were the same event to occur today, at the very least you could expect virtually all power grids and phone lines to not only go down, but burst into flames. From the Wikipedia article:
From August 28, 1859, until September 2, numerous sunspots and solar flares were observed on the sun. Just before noon on September 1, the British astronomer Richard Carrington observed the largest flare, which caused a major coronal mass ejection (CME) to travel directly toward Earth, taking 17 hours. Such a journey normally takes three to four days. This second CME moved so quickly because the first one had cleared the way of the ambient solar wind plasma.
On September 1, 1859, Carrington and Richard Hodgson, another English amateur astronomer, independently made the first observations of a solar flare. Because of a simultaneous “crochet” observed in the Kew Observatory magnetometer record by Balfour Stewart and a geomagnetic storm observed the following day, Carrington suspected a solar-terrestrial connection. Worldwide reports on the effects of the geomagnetic storm of 1859 were compiled and published by Elias Loomis which support the observations of Carrington and Balfour Stewart.
On September 1–2, 1859, the largest recorded geomagnetic storm occurred. Aurorae were seen around the world, even over the Caribbean; those over the Rocky Mountains were so bright that their glow awoke gold miners, who began preparing breakfast because they thought it was morning. People who happened to be awake in the northeastern US could read a newspaper by the aurora’s light.
Telegraph systems all over Europe and North America failed, in some cases shocking telegraph operators. Telegraph pylons threw sparks and telegraph paper spontaneously caught fire. Some telegraph systems continued to send and receive messages despite having been disconnected from their power supplies.
A repeat of this could be something of a civilization-ender. With a universal power grid failure, the factories needed to produce the replacement parts for the trashed grid would themselves be out of power, and very likely damaged. While everything could of course be repaired, the problem would be that the timeframe could be weeks to months before basic utilities are back up and running… and as has often been noted, modern cities are only a few meals away from anarchy. What would New York, Los Angeles or Chicago be like a week after the power goes down, the phones stop working and the food truck stop coming in?
This is one of those unlikely-yet-conceivable events that Doomsday Preppers spend lots of time trouble and treasure fretting about.
Fortunately, unlike an EMP burst from an orbital nuke, this is something that can be seen coming a few hours to a few days out. The proper response would be to issue warnings, and then an hour or so before the pulse gets here… shut down the grids and start physically disconnecting the transformers. It would be unpopular, and it would leave people in the dark for perhaps a few days, but it’s better than having transformers explode and power lines vaporize.
Also fortunately, such events are rare, about once every 500 years.