Sunspots on Parade
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"Halloween Storms of 2003":
Early last week, a large sunspot region caught the attention of many sungazers around the world. Sunspot region 10484 was associated with several powerful solar flares, including one X-class event (the most powerful category). The sunspots in the region covered more than 1700 millionths of the visible solar surface, or 10 times the surface of the entire Earth!
But hold on! Another region, number 10486, was rotating onto the solar disk, showing even more signs of activity. And this particular region had caught the attention of solar physicists while it was still on the far side of the Sun! In the MDI instrument's far side imaging pictures, it showed considerable development over a short period of time. The rapid growth was noted by KehCheng Chu of Stanford University, but the fact was not widely publicised. "The data were a bit scarce, and there was a chance that the images were influenced by this," says Phil Scherrer, Principal Investigator for MDI.
The speculations have since been vindicated by a lot of activity (including even stronger X flares) coming from this new region. On Sunday 26 September 2003, its sunspot area grew to over 2200 millionths, or 13 times the surface of the Earth. And both regions still pack a punch: Both flexed their muscles with X-class flares on Sunday.
Credits: SOHO/MDI, SOHO/LASCO (ESA & NASA)