Tuesday, May 8, 2012

Fun in the Sun: Coronal Holes, CMEs and AR1476

NASA's Solar Dynamics Observatory took this picture of the opening on May 8th.
 Coronal Holes

A dark hole in the sun's atmosphere (a 'coronal hole') is spewing a stream of solar wind toward Earth. The impact of the stream, expected on May 9-11, could add to the effect of the incoming CMEs, boosting the chances of strong geomagnetic activity later this week.

 Coronal holes are places where the sun's global magnetic field opens up and allows some of the sun's atmosphere to escape. The outflow of gas is the solar wind. NOAA forecasters estimate a 40% chance of geomagnetic activity on May 9-10 when the stream arrives (along with the CMEs of May 7th).


A pair of solar eruptions on May 7th hurled coronal masss ejections (CMEs) toward Earth. Forecast tracks prepared by analysts at the Goddard Space Weather Lab suggests that clouds with arrive in succession on May 9th at 13:40 UT and May 10th at 07:54 UT (+/- 7 hours). The double impact could spark moderate geomagnetic storms. High-latitude sky watchers should be alert for auroras.

Amateur astronomer Alan Friedman sends this picture of the behemoth from his backyard in Buffalo, NY.


One of the largest sunspot groups in years rotated over the sun's northeastern limb on May 6th. With a least four dark cores larger than Earth, AR1476 sprawls more than 100,000 km from end to end, and makes an easy target for backyard solar telescopes.

"AR1476 is firecrackler," says Friedman. 

Indeed, the active region is crackling with impulsive M-class solar flares. Based on the sunspot's complex 'beta-gamma' magnetic field, NOAA forecasters estimate a 75% chance of more M-flares during the next 24 hours. There is also a 10% chance of powerful X-flares.

"This one is going to be fun as it turns to face us!" predicts Friedman. He might be right.