An immense area of sunspots large enough to contain 70 earth-size planets had come into view around the eastern rim of the Sun. Created by intense magnetic fields, the giant sunspot group suddenly brightened and expanded to cover hundreds of thousands of square miles. This solar eruption, called a flare, was accompanied by a huge burst of electromagnetic radiation and a large coronal mass ejection. The radiation, mostly in the form of X-rays, traveled at the speed of light and was detected on Earth about eight minutes after the flare erupted. Carried along by the solar wind that blows continuously away from the Sun at speeds of up to several million m.p.h., the energetic particles from this large solar flare happened to intercept Earth in its orbit around the Sun. (Photograph of a large sunspot group courtesy of the Space Environment Center/NOAA.)

Earth has a strong magnetic field that extends far into space. Like a rock in a stream, the solar wind mostly flows around the magnetic cavity called the magnetosphere. During the solar eruptions in March 1989, the solar wind buffeted Earth's magnetosphere resulting in large "magnetic storms." These caused huge auroral displays that extended much farther to the South than usual. They also caused radio interference, increased drag on satellites orbiting near Earth, and were responsible for shutting down the Hydro-Quebec power system that blacked out parts of Montreal and the province of Quebec for as long as 9 hours causing millions of dollars in damages.

The electric power disruptions in Canada and the US during the march 1989 storms are shown in the illustration at right. (Map courtesy of the Electric Power Research Institute.)