AR11339 appeared on the solar NE limb during unstable summer weather in Sydney: some time was needed to capture details in this immense group. A strong and complex penumbra held large elongated umbrae and many smaller spots. Mt Wilson umbral field data (c) Regents Uni. of Southern California has been added to my sketch - revealing the tell-tale signs of a Hale Class Beta-Gamma-Delta group.
This was a big group from the outset: "Helio" freeware, (c) Peter Meadows, showed an area of 1400 units on Nov 3, growing to 1600 on the 4th, probably its peak, and 1200 on the 5th. It was big, too, in longitude length - 18 degrees on November 4, according to the timings. Hale's original system did not include sub-class delta - this was added by Kunzel (1960) and defined as "two or more umbrae of opposite magnetic polarity in a single penumbra" (Zirin, "Astrophysics of the Sun"p335). The Mt Wilson polarities for 2011 November 5 15:30UT show opposite polarities in both the large preceding (p) penumbra (Fig, R21,block arrow) as well as in the following (f) penumbra (V18).
"Delta (class) groups are responsible for almost all great flares" (Zirin and Liggett, 1987)"
The group hosted one GOES class X1.9 flare Nov 3 20:27UT and multiple class M flares during its first few days on the visible disc. Data for Nov 8 showed the polarity mix was no longer present - and flaring had dropped to GOES ~C1. The group will be monitored for any emergence of new flux that may reingnite flaring.
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