The sunspot region, known as AR2192, is so big that it is visible to a (well-protected) naked eye and was visible during Thursday’s partial solar eclipse.
“This is the largest sunspot group since November of 1990,” said Doug Biesecker, a researcher at the National Weather Service Space Weather Prediction Center. Its size is 2,740 millionths of the solar disc which, according to the Web site The Sun Today, is roughly the size of Jupiter.
NASA says the largest sunspot on record, observed in 1947, was almost three times as large as AR2192. Consider that AR2192 is 80,000 miles in diameter – and you could lay 10 Earths across it.
Large sunspot regions often produce elevated solar flare activity, which can be a concern if they’re accompanied by earth-directed CMEs. But Biesecker said that size isn’t everything when it comes to flare severity. Rather, the magnetic complexity of the sunspot region is a better predictor of the potency of the flare.
“A typical sunspot region has a north and south pole but some are are more complex with polarity mixed together,” Biesecker said. “[Sunspot region AR2192] has some of that mixed polarity, but this region isn’t as scary as the region associated with the Halloween solar storm of 2003 which was more complex.”
The 2003 Halloween solar storm was so strong that aurora were visible in Florida, according to NASA.
While this sunspot region doesn’t appear as active as the Halloween 2003 region (which was smaller, but more magnetically complex), in the last week alone it has unleashed 8 M-class flares, and 2 X-class flares – the strongest variety on the flare rating scale.
“If [the sunspot region] maintains this level of complexity, we still believe more X-class flares are likely, and that should continue for next 6 or 7 days,” Biesecker said. “It’s now in position that you would expect any CMEs to be earth-directed for the next 3 or 4 days.”
The aurora hopeful – particularly living at high latitudes – will no doubt be tracking this sunspot region, eager for some action while spacecraft and power grid operators keep fingers crossed CME activity remains depressed.
(This post was updated Friday morning, October 24, after initial publication Thursday afternoon.)