Just did a bunch of research on solar flares after watching Knowing.
That shit is crazy. The largest solar flare that is known to us happened in 2006, on a red giant star called II Pegasi, which unleashed a solar flare engery that equels 50 million trillion (yes, million trillion) atomic bombs, and if it were our sun, it would have definitely killed most if not all life on earth.
The largest solar flare that has ever been recorded from our sun was in 1859, it was so powerful that telegraph systems all over north america and europe failed and started throwing sparks and getting overheated, cathing the telegraph papers on fire.
I'm definitely looking this movie up now.