One out of two isn’t bad — the massive sunspot has produced six X-class solar flares — the strongest type of flare — and more than a dozen M-class flares, the second-strongest type of flare.
Solar flares are very fast and powerful eruptions from the sun’s photosphere. Often they are followed by coronal mass ejections (CMEs), which eject billions of tons of particles out into space where they travel along the solar wind. If directed at Earth, these particles interact with our magnetic field producing northern lights.
READ MORE: Why do we get the northern lights?
But there have been no CMEs with the half-dozen flares.
A CME forms from a prominence, or filament. Along with other elements, gravity has to push it down, while the magnetic field has to push it out. And one of those elements has to give in order to produce a CME.
So, no filament, no CME and no northern lights.
The frustrating part for astronomers — or anyone who is hoping for a great northern lights show — is that a CME was ejected on Oct. 14, just before it turned towards Earth.
Sunspot 2192 does have very active magnetic loops, and though those are closely related to filaments, they just don’t produce the same instability.
Though it was initially believed that this sunspot was the largest in 20 years, Pesnell said that it looks like this is the biggest in 30 years.
The sun goes through a solar cycle roughly every 11 years. This cycle — called Cycle 24 — has been one of the quietest ever, with few sunspots and little activity. Now, the sun is starting to come out of its maximum into its minimum. You might expect it to be less likely that a giant sunspot would form, but it turns out this is the perfect time. That’s because what destroys sunspots is weaker at this stage.
“I was fully expecting to see some larger spots,” Pesnell said. “I was just surprised to see the biggest one in many years.”
Bob Rutledge, lead forecaster for NOAA’s Space Weather Prediction Center said that there’s been a debate as to whether or not it’s unusual for a sunspot of this size to produce so many solar flares with no CMEs.
“I wouldn’t have bet you we could have half a dozen X-class flares and not get any radiation storm or any significant CME activity,” Rutledge said.
“It’s certainly unusual, I wish I could tell you why.”
It takes about 27 days for a sunspot to make one trip around the sun. We get to see it for about half of that time (though numerous spacecraft keep an eye on it when out of Earth’s view). Though sunspot 2192 shrunk slightly a couple of days ago, it has since rebounded. And this means that it’s likely to survive its trip around the sun, meaning we might see it again.
A history of coronal mass ejections
In March 1989, a sunspot produced a solar flare and subsequent major CME that, when it reached Earth, knocked out most of Quebec’s power grid, leaving the province in darkness for almost 12 hours.
READ MORE: How solar storms could leave us in the dark
And that sunspot was smaller than this one.
It’s these events that lead heliophysicists — scientists who study the sun — to probe ever-deeper into the dynamic nature of the sun, because the interactions of the various elements — like sunspots, filaments, loops — still isn’t completely understood.
Pesnell said that he’s not worried that this sunspot could result in a Carrington-like event, where a major solar flare and CME struck Earth in 1859, setting telegraph poles afire and resulting in an incredible display of northern lights.
(If something of that magnitude happened today, with our reliance on electronics and satellites, it could have devastating effects on our everyday lives.)
Major solar flares can pose a danger to satellites as well as astronauts aboard the International Space Station.
But an email from NASA said that the agency is always monitoring solar activity and that teams have decided that no special action was needed.
So, though the sunspot isn’t producing activity enough to trigger the northern lights, it’s giving scientists the opportunity to study a unique event.
“I think this is nice because it’s an odd duck,” Pesnell said. “And whenever you have something that’s a little different, that’s where you start learning about how these complicated systems work.”
“We still have a lot to learn.”