The solar storm of 1859, the largest…
September 1859 CE
The associated "white light flare" in the solar photosphere is observed and recorded by British astronomers Richard C. Carrington (1826–1875) and Richard Hodgson (1804–1872).
A solar storm of this magnitude occurring today would cause widespread electrical disruptions, blackouts and damage due to extended outages of the electrical grid.
The solar storm of 2012 will be of similar magnitude, but it will pass Earth's orbit without striking the planet, missing by nine days.