Mystery of the Missing Sunspots, Solved?
June 18, 2009 by Dr. Tony Phillips
A helioseismic map of the solar interior. Tilted red-yellow bands trace solar jet streams. Black contours denote sunspot activity. When the jet streams reach a critical latitude around 22 degrees, sunspot activity intensifies.
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.
Rachel Howe and Frank Hill of the National Solar Observatory (NSO) in Tucson, Arizona, used a technique called helioseismology to detect and track the jet stream down to depths of 7,000 km below the surface of the sun. The sun generates new jet streams near its poles every 11 years, they explained to a room full of reporters and fellow scientists. The streams migrate slowly from the poles to the equator and when a jet stream reaches the critical latitude of 22 degrees, new-cycle sunspots begin to appear.
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. Shifting masses inside the sun send pressure waves rippling through the stellar interior. So-called "p modes" (p for pressure) bounce around the interior and cause the sun to ring like an enormous bell. By studying the vibrations of the sun's surface, it is possible to figure out what is happening inside. Similar techniques are used by geologists to map the interior of our planet.
In this case, researchers combined data from GONG and SOHO. GONG, short for "Global Oscillation Network Group," is an NSO-led network of telescopes that measures solar vibrations from various locations around Earth. SOHO, the Solar and Heliospheric Observatory, makes similar measurements from space.
"This is an important discovery," says Dean Pesnell of NASA's Goddard Space Flight Center. "It shows how flows inside the sun are tied to the creation of sunspots and how jet streams can affect the timing of the solar cycle."
There is, however, much more to learn.
"We still don't understand exactly how jet streams trigger sunspot production," says Pesnell. "Nor do we fully understand how the jet streams themselves are generated."
To solve these mysteries, and others, NASA plans to launch the Solar Dynamics Observatory (SDO) later this year. SDO is equipped with sophisticated helioseismology sensors that will allow it to probe the solar interior better than ever before.
"The Helioseismic and Magnetic Imager (HMI) on SDO will improve our understanding of these jet streams and other internal flows by providing full disk images at ever-increasing depths in the sun," says Pesnell.
Continued tracking and study of solar jet streams could help researchers do something unprecedented--accurately predict the unfolding of future solar cycles. Stay tuned for that!
Source: Science@NASA
2 hours ago
I would say that assumption is in line with the unstated views of the researchers.
Agreed. An interesting comment PinkElephant.
Solar surface surface activity is an indication of deep-seated magnetic fields protruding through the visible solar surface as sunspots.
These magnetic fields accelerate a stream of protons upward from the solar core, where the protons are produced by neutron-decay.
The upward flow of protons is the carrier gas that maintains mass separation of elements and isotopes in the Sun.
When ordinary stars enter a long period with no sunspot activity, like the Maunder Minimum, mass fractionation is diminished and the stellar surfaces become iron-rich.
This was predicted in a 2002 paper ["Superfluidity in the solar interior: Implications for solar eruptions and climate," Journal of Fusion Energy 21 (2002) 193-198] and observed in a 2004 UC-Berkeley survey of Maunder Minimum stars: http://tinyurl.com/nkpylz
With kind regards,
Oliver K. Manuel
http://www.omatumr.com
*SMACK*
Ouch the IPCC just hit me.
Let's face it, they're trying to do a 'weather' forecast for a body 93 million miles away! Look at how much trouble we have with long-term forecasts down here on Earth.
BOULDER%u2014The next sunspot cycle will be 30-50% stronger than the last one and begin as much as a year late
...
expect the cycle to begin in late 2007 or early 2008 ...
I would say there is much to be discovered in the future.
Regarding Pink's comment: It will be very interesting to see if this cycle lasts longer or if the stream gets "snapped" back up north more quickly as it comes into conflict with the underlying forces that cause the cycle.
Anyone know of any good sites, like spaceweather.com where we can keep tabs on this?