Imagine you're in California. It's July, the middle of summer. The sun rises early; bright rays warm the ground. It's a great day to be outside. Then, suddenly, it begins to snow--not just a little flurry, but a swirling blizzard that doesn't stop for two weeks. That's what forecasters call unseasonal weather. It sounds incredible, but "something like that just happened on the sun," says David Hathaway, a solar physicist at NASA's Marshall Space Flight Center. Only a few weeks ago solar activity was low. The face of the sun was nearly blank--"very few sunspots," says Hathaway--and space weather near Earth was mild. "Mild is just what we expect at this point in the 11-year solar cycle," he explains. "The most recent maximum was in 2001, and solar activity has been declining ever since." Then, suddenly, in late October the sun began to behave strangely. Three giant sunspots appeared, each one larger than the planet Jupiter. In California where smoke from wildfires dimmed the sun enough to look straight at it, casual sky watchers were startled by the huge blotches on the sun. One of them, named "sunspot 486," was the biggest in 13 years.

Sunspots cause solar flares and, usually, the biggest flares come from the biggest spots. The three giant sunspots unleashed eleven X-class flares in only fourteen days--equaling the total number observed during the previous twelve months. "This was a big surprise," says Hathaway. The effects on Earth were many: Radio blackouts disrupted communications. Solar protons penetrated Earth's upper atmosphere, exposing astronauts and some air travelers to radiation doses equal to a medical chest X-ray. Auroras appeared all over the world--in Florida, Texas, Australia and many other places where they are seldom seen.

View: Full Article | Source: Nasa.gov