The magnetic field of the earth was struck by a Coronal Mass Ejection from the sun during the evening of March 10th, 2011.
Just after 11:15 P.M. the CME sparked very bright Northern Lights over Minnesota. The aurora was just a green glow on the horizon
until it looked like someone flipped a switch and turned on the lights to become bright enough to cast a shadow for a few minutes.
The Aurora event peaked about the same time as the earth quake in Japan before Midnight local time in Minnesota.