NASA scientists watching the sun are bracing for a big jump in solar activity as the quietest period in decades comes to an end.

In 2008, the solar cycle, marked by the ebb and flow of sunspots, fell to its deepest trough in nearly a century. But lately the number of sunspots, solar flares and spectacular coronal mass ejections has gone up. Increases in solar activity mean that the auroras will be visible more often and further south than usual. It also means that there is more chance of damage to satellites and danger to astronauts.

The sun has an 11-year cycle, and there have been two dozen recorded since the 18th century. The most recent cycle, number 24, was unusual because there were no sunspots at all. While that has happened before, this time the disappearance of sunspots lasted longer than it usually does.

The first signs that the sun was returning to its more usual self were when Earth orbiting satellites detected a pair of X-class solar flares--the most powerful kind of x-ray flare. One appeared on Feb. 15, and the next on March 9. The last such eruption occurred in December 2006.

The Marc flare shot a billion tons of plasma away from the sun at 5 million miles per hour, or about 1,400 miles per second. The rapidly cloud wasn't aimed directly at Earth, but it did graze the Earth's magnetic field on March 10. Even that was enough make Northern Lights visible as far south as Minnesota, Wisconsin and Michigan.

That was the fastest coronal mass ejection in almost six years, said Angelos Vourlidas of the Naval Research Lab in Washington D.D., in a statement. To me this marks the beginning of Solar Cycle 24.

The video clip shows the large X2 flare seen by Solar Dynamics Observatory (SDO) in extreme ultraviolet light on February 15, 2011, has been enlarged and superimposed on a video of SOHO's C2 coronagraph for the same period. This was the largest solar flare since December 5, 2006. The coronagraph images show the faint edge of a halo CME as it raced away from the Sun and began heading towards Earth. The video covers about 11 hours.