|Solar Flare erupting from the sun, from October 2003. |
How are solar flares classified? They're measured by satellites above the earth, which look to quantify the flux...the unit being Watts per square meter. So the class rankings (from weakest to strongest) are A, B, C, M, X. They're similar to earthquakes, in that each class up represents a 10-fold increase in strength of the flare. For example, an M class solar flare is 10 times stronger than a C class flare. Classes A through C generally have minimal to no impact here on Earth. M class can have minor impacts, mainly at the poles. X class flares are the big boys though, and they can pack the punch and cause the problems. BUT...just because a solar flare is X-class does not mean it's going to destroy the electrical grid...as you might think from watching the news every time there is an X class flare.
|Visible auroras: A fairly common result of solar flares|
and CMEs. This, from 2003. Credit: NASA
There's no way to know how strong it was, but the 1859 Carrington Event solar flare would dwarf any solar event in modern history. The Carrington Event produced a visible aurora as far south as the Caribbean, destroyed telegraph lines, and produced auroras bright enough in the Northeast to allow people to read newspapers at night. The Carrington Event is the main reason we've seen such dire news stories in recent years describing how serious solar storms can be. A dose of reality though: While certainly possible again in the future, an event of the magnitude of a Carrington Event is extraordinarily rare...and in hundreds of years of observations, it has only occurred once. While solar flares are important to study and prepare for, you needn't panic about it every time one occurs.