Wednesday, 18 July 2012

AR11520: southern giant!

The sketch shows AR11520 on July 13 - the biggest group of SC24 IN THE SOUTH. It had an area about 1400 units - still smaller than northern group AR11339 in 2011 that reached 1600 units. Still it was a giant, stretched across twenty degrees longitude, and easily seen with the PROTECTED but unaided eye!
     Here we see the two dominant red spots surrounded by lesser violet ones. The boundary between is termed the inversion line - and separates fields of opposite polarity. A dark active region filament there with a ring of bright plage 'cocooned' the main spots. This was the site of major flares - though cloud and time-zone meant I saw only some modest C-class events. The group was to have a long-lived M class at the west limb five days later, producing fine post flare loops. This group is the second transit of AR11504 (June) - will there be a third in two weeks time?