Spooky Sun



We usually think of our Sun as being one of the more boring stars in the neighborhood. Pretty average mass, pretty stable, a constant feature of our lives. But, with Halloween approaching the Sun is getting on the scary act. Our local star was active all weekend long, producing three of the most intense solar flares possible in two days.

The sun is currently at the peak of its natural 11-year solar cycle, where it oscillates through periods of low activity — characterized by few sunspots and intense flares — and much higher activity. This particular solar cycle has been one of the quietest on record, with the sun occasionally even going completely silent just as its activity should be highest. This weekend’s flares are a return to the normally scheduled intense outbursts from the solar surface that typically characterize solar maximum.

The first flare, which occurred on Oct. 25, was classified as an X1.7 class flare. An X-class flare is the strongest category of solar flare, where massive amounts of radiation spew from the sun’s surface. If this radiation is directed at Earth, it can mess with satellite communication, create radio blackouts, and generate beautiful auroras. An even more intense flare, an X2.1 flare, burst from the sun seven hours after the first on Oct. 25. An X2-class flare is twice as intense as an X1. A third flare X1-class occurred on Oct. 27 and at least 15 additional lower M-class flares happened between Oct. 23 and Oct. 28. Check out the video above for the latest ‘space’ weather forecast.


Here comes the Sun



The sun has unleashed three strong solar flares since Sunday evening, punctuating a short period of increased solar restlessness that comes as scientists are keeping an eye out for this cycle’s solar maximum. All were X-flares, classified in the category of most intense solar activity. None was pointed at the Earth, though several spacecraft, including the Spitzer space telescope in particular, are in their path.

Each was the most energetic solar flare of 2013 — until the next one came along. The first, an X1.7, occurred around 10 p.m. U.S. Eastern time, on May 12. Then, an X2.8 erupted at 12:05 p.m. on May 13. And the last one, an X3.2, peaked at 9:11 p.m. on May 13. X3.2 is the third-largest flare of this solar cycle, with the largest being an X6.9 in 2011.

“Current estimates are for a 40 percent probability of another X flare during the next 24 hours,” said Alex Young, a heliophysicist and associate director for science in NASA’s heliophysics division. He calculated that each of the flares produced around 100 sextillion (that’s 10 followed by 23 zeros) Joules of energy – the equivalent of 100 million hydrogen bombs – and spat several billion tons of solar material into space. The sunspotted region producing the flares is just rotating into view. Within a week, they’ll be pointed squarely at us – and scientists will be able to get a good look at the turbulent spots, which Young estimates are several Earths across. “We’ll watch it to see if it’s continuing to grow in size, or if it’s starting to get smaller,” he said.

Flares of X-magnitude are multi-stage events, produced by sunspotted regions where magnetic fields are twisted and tangled, knotted and strained like rubber bands wound too tightly. Eventually, strain building up causes the magnetic field lines to snap, releasing a flare. “If you look on the sun, you’ll see some very symmetric-looking, simple sunspots. These are the ones that don’t really do anything, even if they’re really big,” Young said. “But if you look at sunspots like the one that’s been so active, it’s very complicated and very twisted. You would probably see rotation and a lot of jumbled mess. That’s a really strong indication that it’s got a lot of energy built up in it.”

This period of unrest comes as scientists are keeping an eye out for the solar maximum, a period of peak activity that occurs at the height of the 11-year solar cycle. Forecast to be a relatively quiet maximum, the peak should be occurring just about now, though it’s hard to define a peak until it’s passed. An earlier period of peak activity occurred in 2011, but Young suggests that asynchronous activity in the sun’s northern and southern hemispheres can produce twin-peaked maxima. “That’s something we’ve seen in the past, with many different solar cycles,” he said.