Thursday, 25 April 2013

Big flare in AR11718

AR11718, a northern hemisphere group, was a simple entity at first. Around April 9, half way across the disc, it had a burst of new spots: a close count showed about 30, many in curved chains. It seemed  two spot groups were intertwined - and the complexity implied fireworks! On the 10th and 11th it was almost too complex to sketch. Here we see it on the 12th when it had an M3.3 flare. The peak was at local sunrise (20:38UT) and I had this view at 20:49UT when the GOES flux had dropped to M1.  It was a great flare - bright and of large area: ~450 area units, roughly the size of the spots themselves. The group stretched across nine degrees of longitude, and at the time lay some 40 degrees from the western limb.      This was one of the few great flares in AR11718. Nearby, AR11719 had an M6.5 on the 11th at 07:16UT, not seen in Sydney.