* Astronomy

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Solar activity

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RE: Sunspots

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Solar Cycle Driven by More than Sunspots
Challenging conventional wisdom, new research finds that the number of sunspots provides an incomplete measure of changes in the Sun's impact on Earth over the course of the 11-year solar cycle. The study, led by scientists at the National Centre for Atmospheric Research (NCAR) and the University of Michigan, finds that Earth was bombarded last year with high levels of solar energy at a time when the Sun was in an unusually quiet phase and sunspots had virtually disappeared.

"The Sun continues to surprise us. The solar wind can hit Earth like a fire hose even when there are virtually no sunspots" - lead author Sarah Gibson of NCAR's High Altitude Observatory.

The study, also written by scientists at NOAA and NASA, is being published today in the Journal of Geophysical Research. It was funded by NASA and by the National Science Foundation, NCAR's sponsor.

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Sunspots are a bit of a mystery. They appear as dark patches in the photosphere - the surface layer of the sun - that come and go. Normally the number of sunspots peaks every 11 years, coinciding with times when the sun's magnetic field is at its strongest. As the field wanes, the number of sunspots falls to a trough at which point the sun's magnetic field reverses direction and starts to regain its strength.
As early as 1801 William Herschel, a British astronomer, suggested that when sunspots were plentiful the Earth would be warmer. He supported his hypothesis by reference to variations in the price of wheat published in Adam Smith's "Wealth of Nations".
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Are Sunspots Disappearing?
The sun is in the pits of the deepest solar minimum in nearly a century. Weeks and sometimes whole months go by without even a single tiny sunspot. The quiet has dragged out for more than two years, prompting some observers to wonder, are sunspots disappearing?

"Personally, I'm betting that sunspots are coming back" - researcher Matt Penn of the National Solar Observatory (NSO) in Tucson, Arizona.

Penn's colleague Bill Livingston of the NSO has been measuring the magnetic fields of sunspots for the past 17 years, and he has found a remarkable trend. Sunspot magnetism is on the decline.

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Sunspots stir oceans
Computer simulations are showing how tiny variations in the Sun's brightness can have a big influence on weather above the Pacific Ocean.
The simulations match observations that show precipitation in the eastern Pacific varies with the Sun's brightness over an 11-year cycle. However, the model does not indicate a relationship between solar activity and the rise in global temperature over the past century.

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Centuries-old sketches solve sunspot mystery
A second look at sunspot drawings from the 1700s has clarified a puzzling episode in the sun's history, and could lead to more accurate forecasts of dangerous solar outbursts.
The sun sometimes hurls clouds of plasma our way, which can fry satellites and knock out power grids on EarthMovie Camera. The outbursts are most common during solar maxima, when the dark blemishes of sunspots appear in greatest abundance on the sun.
Although there is an average of 11 years between solar maxima, predicting the exact timing and height of each peak is difficult as there is little historical data to plug into models. About two dozen solar cycles have occurred since reasonably complete records began. Now an analysis of historic sunspot drawings suggests that this patchy record had omitted a solar cycle from the late 1700s.

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An international team of scientists led by the National Centre for Atmospheric Research (NCAR) has created the first-ever comprehensive computer model of sunspots. The resulting images capture the necessary scientific detail but highlight a remarkable, usually unseen beauty.
So far, scientists have determined that sunspots are linked with massive ejections of charged plasma that can cause extremely powerful geomagnetic storms that can disrupt communications and navigational systems.

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Bad weather is on the way and scientists are relieved. It is not the type that the weather bureau tips will bring more showers to Sydney today and tomorrow - it is space weather, born beneath the sun's surface.

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Mystery of the Missing Sunspots, Solved?
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.

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