The explosion sent out a massive interplanetary shock wave that triggered a severe geomagnetic storm in Earth's atmosphere the next day and blacked out some radio communications. Spectacular auroras were visible in the sky across much of North America and Europe. The storm was the strongest yet in a series of outbursts that have raged on the Sun since early in the year. The July 14 blast came from an active sunspot region numbered 9077. It is one of more than 200 sunspots that have been visible on the Sun's surface in recent weeks.
Sunspots are relatively cool areas that appear as dark spots on the solar surface.
Like clockwork, the Sun goes through a cycle of increased and decreased sunspot activity every 11 years. In 2000-2001, the cycle is at its peak. The reason why the Sun's magnetic field goes through an 11-year cycle remains one of the great mysteries of solar astronomy. Geomagnetic storms in Earth's atmosphere occur when the particles, radiation, and solar wind created by sunspots compress Earth's magnetic field more than usual. In years when there are more sunspots, the number of geomagnetic storms increases.