Tuesday, June 23, 2009

Where have all the sunspots gone, and why?

For the past 3 years, sunspot activity has been greatly reduced. I came across this article recently, that offers an explanation as to why this is so:

Mystery of the Missing Sunspots, Solved?
June 17, 2009: The sun is in the pits of a century-class solar minimum, and sunspots have been puzzlingly scarce for more than two years. Now, for the first time, solar physicists might understand why.

At an American Astronomical Society press conference today in Boulder, Colorado, researchers announced that a jet stream deep inside the sun is migrating slower than usual through the star's interior, giving rise to the current lack of sunspots.


Howe and Hill found that the stream associated with the next solar cycle has moved sluggishly, taking three years to cover a 10 degree range in latitude compared to only two years for the previous solar cycle.

The jet stream is now, finally, reaching the critical latitude, heralding a return of solar activity in the months and years ahead.

"It is exciting to see", says Hill, "that just as this sluggish stream reaches the usual active latitude of 22 degrees, a year late, we finally begin to see new groups of sunspots emerging."

The current solar minimum has been so long and deep, it prompted some scientists to speculate that the sun might enter a long period with no sunspot activity at all, akin to the Maunder Minimum of the 17th century. This new result dispells those concerns. The sun's internal magnetic dynamo is still operating, and the sunspot cycle is not "broken."

Because it flows beneath the surface of the sun, the jet stream is not directly visible. Hill and Howe tracked its hidden motions via helioseismology. [...]

It shows how the current cycle has dragged on for a year longer than usual, but also goes on to explain why that is about to change soon. It also explains more about helioseismology, and NASA's upcoming launch of the Solar Dynamics Observatory (SDO), which will provide us with more information about the sun. Interesting stuff.


Anonymous said...

hmmm... well... it's 2 months later... and it's been 39 days since the last sunspot. Ok... We just need to wait a little longer... another Month... ummm.. Year... ummm.. Decade maybe????

We'll see!

Chas said...

Yes, indeed we will. I've seen some arguments where some people are questioning if the new cycle has even really started yet. It was predicted to be a weak cycle, but it's not like we've got it all figured out, either.

Sometimes it seems like the more we learn, the more we don't know. I find the theories about how the sun works, and the reasoning behind them interesting, but there is still a great deal we don't understand.