Solar flares: flashes with a twist

Sunspot 930 (dark area) and associated
X-class solar flare of 12/13/06 (bright).
Image Credit: Hinode, Japan Aerospace Exploration
Agency (JAXA).The Sun doesn't usually make the headlines--not even something like, "Flash! Nuclear explosion as powerful as a billion H-bombs sighted only 93 million miles from Earth!"

Let's face it, things like that just don’t seem relevant to our everyday lives. The Sun may be the nearest star, but it still lies at a distance that would take you well over 3000 years to walk, if you could. What happens on the Sun, stays on the Sun, right?

Wrong.

Take Sunspot 930 as an example. Last December, this prominent spot came into view and moved across the Sun's face, carried by the Sun's rotation and marking the location of intense magnetic activity, of which sunspots are a side-effect.
The sunspot itself was equivalent in size to two or three Earths--which is not unusual; the Sun is a big object, and just about everything that goes on there is done in big fashion.

As the magnetic fields twisted and turned, energy built up in them, similar to how tension builds up in a rubber band when you twist it tighter and tighter.

At some point, all that wound up magnetic energy reached a sort of breaking point, and things simply "snapped." Enormous quantities of energy that had been held in the magnetic field was released into the surrounding gases of the solar atmosphere, causing a rapid and unimaginably violent explosion of heat and radiation.

A solar flare was unleashed--and in this event, back on December 13, 2006, one of the most powerful types: an "X-class" flare. More details and animations of this event can be found at this link:

http://www.chabotspace.org/vsc/solar/hinode/discovery/highlights/2006-1213-flare.asp

In fact, Sunspot 930 produced three powerful X-class flares in December: one on December 5th, then the December 13th flare, and finally one on the 14th.

The gases of the flare were heated to 20 million degrees or more, and a burst of intense gamma rays and X-rays flashed out across the solar system, reaching Earth only 8 minutes later. In the picture above, the bright, slinky-shaped structure below the sunspot is the flare and its impelling magnetic fields.

While the X-rays and gamma rays were blocked from reaching the ground by our atmosphere, our planet doesn't go completely unscathed by solar outbursts. Both solar flares and another type of eruption called a coronal mass ejection can affect Earth in a number of interesting ways, including the production of spectacular aurora displays in the polar regions, radiation storms in the spaces around the Earth that can pose a threat to astronauts and Earth-orbiting satellites, and geomagnetic storms—disturbances in Earth’s magnetic field that can deflect compass needles and induce blackouts in electrical power grids.

You can check out the current and recent conditions of "space weather" caused by the Sun at Spaceweather.com.

Currently, the Sun is in the middle of a "quiet" period of a cycle of magnetic activity it undergoes every 11 years. As we move away from the bottom of this cycle, however, look for reports of solar activity—sunspots, solar flares, geomagnetic storms, and the like—to be on the rise, reaching a crescendo sometime around 2012 or 2013.

Benjamin Burress is a staff astronomer at The Chabot Space & Science Center in Oakland, CA.