When the charged particles slam into the earth's magnetic field they create a spectacular light show of northern and southern lights. But the charged particles can also disrupt communications, knock out satellites, damage the electric power grid, and expose astronauts and airline passengers alike to extra-high levels of solar radiation. The last time the sun acted so violently, in 1989, radiation blacked out the Hydro-Quebec electric power system, leaving 6 million people in Canada without power for more than nine hours. Sunspots are caused by powerful distortions in the sun's magnetic field which slows the flow of heat from the Sun's interior. Because they are slightly cooler than their surroundings, sunspots appear dark to the eye.
Sunspots usually presage stormy solar weather.
By Mar. 28, the new sunspot, designated AR 9393 by astronomers and the biggest since 1991, was like a giant thunder cloud covering an area equivalent to the surface of 14 earth's. Over the next two days, four huge flares erupted near the sunspot. The first reached Earth early on the morning of Mar. 31, triggering a geomagnetic storm that produced spectacular northern lights visible as far south as Texas and Northern Mexico. Instead of intensifying the storm, the interacting magnetic fields seemed to have neutralized each other. Although no damage was reported, astronomers believe that the show of this solar max is far from over.