The research is fresh and the hypotheses are fluid when it comes to knowing the Sun

This diagram of the Sun's internal structure shows the Sun's major parts, including the jet streams believed to be linked with sunspots. The jet streams extend deep into the Sun, to the base of the solar convective zone. Courtesy of AAS.

I was the only journalist who attended a press conference in person today at the American Astronomical Society’s Solar Physics Division meeting in Boulder (several others participated by phone). I’m attending just because I happen to live here, as of two weeks ago. What a rare treat!

The meeting is a hotbed of brand new insights into the Sun’s recent odd behavior. As a division meeting, it is mostly a sharing of information between working solar physicists, not necessarily an outreach event.

But the buzz here is running parallel to a very hot topic lately in public spheres: the unexpected and perplexing lull between the end of the Sun’s Solar Cycle 23 and the beginning of Solar Cycle 24. Our Sun should have started stirring again after a predicted minimum between the cycles, last year. But until recently — as in, last month — it was mum.

Sunspots, courtesy of AAS.

Over the course of an 11-year cycle, the Sun should see a pattern of sunspots that starts out slow and ramps up to a peak about halfway through. This has been a more or less predictable pattern for ages, with the notable exception of the Maunder Minimum in the 17th Century, an extended era of depauperate sunspots that coincided with a “Little Ice Age” in Europe and other parts of the world.

A NASA and NOAA-supported panel announced just last week that a similarly extreme minimum is unlikely. I wrote a story at National Geographic News about it (here).

During a series of talks at this AAS meeting yesterday — and in the press conference today — solar physicists are eagerly proposing explanations for the recent oddly extended minimum, which appears to have caught everyone off guard. (In fact, the mood here is a bit charged. As I write this, there’s a heated scientific dialogue happening following a talk.)

One promising observation, and the topic of today’s press conference, is that a solar jet stream deep inside the Sun has been migrating more slowly than usual through the star’s interior and it’s at least associated with — if not causing — the current lull in sunspots and solar activity.

Rachel Howe and Frank Hill, both scientists with the National Solar Observatory (NSO) in Tucson, Arizona, used long-term observations from the NSO’s Global Oscillation Network Group (GONG) facility to detect and track an east-to-west jet stream, known as the “torsional oscillation,” at depths of ~1,000 to 7,000 km (about 600 to 4,000 miles) below the Sun’s surface.

The Sun generates new jet streams near its poles every 11 years; the streams migrate slowly, over a period of 17 years, to the equator and are associated with the production of sunspots once they reach a critical latitude of 22 degrees. Howe and Hill found that the stream associated with the new solar cycle has moved sluggishly, taking three years to cover a 10-degree range in latitude compared to two years for the last solar cycle, but has now reached the critical latitude.

I posted more information about the finding, from an AAS press release, at Universe Today and you can read it there.

Hill is confident about the predictive powers of the torsional oscillation:  ”We are now beginning to see Solar Cycle 24 really take off, and the rise to solar maximum is on the way,” he said during the press conference.

But what’s also clear is that the observations are young — with unbroken data dating back only to 1995, when GONG and the Solar and Heliospheric Observatory (SOHO) went online.

As for the relationship of the torsional flows and sunspots, “It’s not clear whether this is a cause or a consequence of them,” Hill said. “But the fact that we see it a couple of years in advance makes me think it’s a cause.”

And the observations are so new, that some solar physicists — at least the ones sitting at the table in the press conference — wish they’d seen them earlier.

“We could have seen that this was coming,” Hill said of the Sun’s lull.

Jesper Schou, from Stanford University, did see it coming — in space observations from SOHO. He and others just weren’t confident about what they were looking at.

“You need some amount of confidence” to know you’re seeing what you’ve seen before, Schou said. “After a while it’s like, oh, it looks very obvious.”

Dean Pesnell, prinicpal investigator on NASA’s Solar Dynamics Observatory (SDO) set to launch this fall, said the ultimate goal is to predict space weather, as a way of giving advanced warning to satellite and GPS systems, astronauts and even airplane routing, all of which can be affected by space weather stemming from the Sun.

I’ll leave you with this solar action movie, courtesy of the AAS. And special thanks to Craig DeForest, the Solar Physics Division press officer, who was very understanding when I accidentally broke the embargo at Universe Today. Yikes; gotta get used to my new time zone!