Wednesday, 20 April 2011
AR11158 and the Biggest Flare for SC24 (so far!)
AR11158 and the Biggest Flare for SC24 Sunspots are interesting things: perhaps they best resemble an Earthly cyclone, if we can imagine a magnetic storm with opposite polarities in contact. AR11158 hosted the largest flare so far for Cycle 24 (SC24), a GOES X2.2.
It seems this group resulted when a normal bipolar group, minding its own business, found another group arising in its midst! This caused much sunspot rearrangement and field complexity - that led to the big flare, and lots of lesser ones. The Mt Wilson magnetogram shows the merging in progress - sunspots are seen in the bright green and yellow "cores" where the umbral fields are about 2300 gauss (in the visible band). The complex central spots have mixed polarities in a single penumbra. There is a nice animation of this online (SDO data perhaps). My sketch shows the group about two hours before the big flare, when cloud ended viewing.
SDO animation http://www.youtube.com/watch?v=U0Lt3SgiEQ8&NR=1