Geomagnetic Storm Watch / New Big Sunspot Turns into View off the East Limb (+Video)

GEOMAGNETIC STORMS: A co-rotating interaction region (CIR) struck Earth’s magnetic field on Dec. 15th, followed shortly thereafter by a high-speed stream of solar wind. The double jolt sparked aG1-class geomagnetic storms and auroras around the Arctic Circle.
More auroras are in the offing on Dec. 15th. NOAA forecasters estimate a 60% chance of continued storming as the solar wind continues to blow.   http://spaceweather.com/

Solar Wind Speed: 503 km/sec.  
Solar Wind Magnetic Fields: Bt 5 nT, Bz 3 nT
http://www.swpc.noaa.gov/

A new sunspot region numbered 2470 turns into view off the east limb. The region has been fairly quiet during the past several hours but will likely remain a threat for an isolated moderate M-Flare.  
AR2470 is large and has a magnetic field that harbors energy for significant explosions. NOAA forecasters estimate a 15% chance of M-class flares on Dec. 15th
http://www.solarham.net/

Co-rotating interaction region (CIR) 
As the wind expands radially, the flow follows the same spiral pattern, but fast wind “catches up” to slow wind and crashes into it. At the interface between the fast and slow wind, a large pressure pulse forms and eventually steepens to create a forward and reverse shock pair. The thin boundaries separating the streams are called co-rotating interaction regions or CIRs.
http://spacephysics.ucr.edu/index.php?content=solar_wind/sw/swq3.html

Image credit: NASA