Solar superflares are infrequent but can be damaging. The worst on record took place in 1859. Most send out a burst of X-rays and a "coronal mass ejection", a burst of charged particles with an embedded magnetic field. The 1859 "Carrington event" caught the attention of naked eye observers, set paper in telegraph offices on fire, and caused the aurora to be seen in Cuba. For a fuller discussion we refer you to NASA.
We conducted a simulation of the atmospheric effects of the Carrington event.
We found there should have been substantial atmospheric ionization, and moderate
ozone depletion rather similar in intensity to what we have experienced
recently from chlorofluorcarbons. The predicted deposition of nitrates in
Greenland ice cores as the atmosphere cleans itself is in good agreement with
data. This was published in
Letters in 2007.
News articles still available on the web from this work are to be found
and the New Scientist.
We continue to be fascinated in the possibility of much more intense Solar flares. There does exist a candidate mechanism which would suggest we are not likely to see such events from our own Sun.
Still, Carrington-like events pose a serious
threat to a technological