The Sun 5

A solar flare is a burst of energy that emerges from sunspots which form on the surface of the sun.

Flares are divided into five categories, based on the amount of energy they emit. These are classes A, B, C, M and X. An X-2 class flare is twice as powerful as an X-1 class flare, and four times more powerful than the highest M-class flare, an M-5, X-class flares up to the power of a November 2003 X-28 explosion have been recorded. It is fortunate that this flare just grazed Planet Earth, because it was later graded as a possible X-45, which would have made it even larger then a 1859 flare called the Carrington Event, which did strike Earth. Were a similar flare to hit us tomorrow, the results would be devastating. In 1972 a solar flare caused the entire Illinois telephone system to shut down due to a power overload, and led AT&T to redesign its transatlantic cable system to reduce the chance that sun-induced overloads could shut it down. On March 16, 1989, a geomagnetic storm took place following a solar flare that was only 16 percent as powerful as the Carrington Event. Because of the way it struck the earth, this minor storm shut down the entire Quebec power grid, leaving the six million customers of Hydro-Quebec without power for nine hours. Some customers remained without power for as long as two months. In New Jersey, a $36-million-dollar transformer was destroyed, causing a nuclear plant to shut down for a short time, and radio transmissions across the northern U.S. and Canada were disrupted, sometimes in bizarre ways. In the upper Midwest, listeners found their radio stations drowned out by transmissions from the California Highway Patrol. In 2003, another solar flare led to a geomagnetic storm that destroyed fourteen huge power transformers in South Africa, hampering that country's electrical grid for years.

Solar Flares: What You Need to Know: A Special from Tarcher/Penguin
by Whitley Strieber

Chapter 1, Solar Flares