Sunspot activity

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http://www.abc.net.au/science/articl...08/2538378.htm

Sunspot activity hits a new low
Wednesday, 8 April 2009 Marilyn Head
ABC


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Astronomers say the sun is experiencing is a very deep solar minimum, but it is still completely within the bounds of what is normal (Source: NASA)

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Solar observers are keeping a close eye on the sun as it experiences its quietest period in more than a century.

While none are concerned by the lack of sunspots, the 'deep solar minimum' is unique opportunity for astronomers to observe our nearest star.

Dr Sean Oughton, an associate professor of mathematics at New Zealand's Waikato University, says the sun's lack of solar activity is expected.

"What we are experiencing is a very deep solar minimum, but it is still completely within the bounds of what is normal," he says.

Flipping out
Oughton says sunspot activity follows 11-year cycles, which are linked to the sun's magnetic field.

When the number of sunspots reaches its maximum the polarity of the sun's magnetic field 'flips'.

According to NASA's Space Weather website the sun is in the middle of a solar minimum, with 266 sunspot-free days last year - the lowest for nearly a century.

In 2009, the sun has been blemish-free for more than 80 days, putting it on track for an even quieter year.

Record reductions in the solar wind, solar radio emissions and solar brightness have also attracted attention.

The reduction in sunspot activity has also seen a drop in solar flares and coronal mass ejections. These events blast vast quantities of atoms and ions into space, disrupting communications systems on earth and threatening astronauts in space.

A drop in solar activity allows more cosmic rays from outer space to enter the solar system.

But it's too soon for us to be worried, says Oughton.

"The solar wind is in fact so gentle that if you could bottle it up and release it next to a tree, the leaves wouldn't even tremble," he says.

Oughton says that even if more cosmic rays enter the solar system, the earth is protected by its own magnetic field.

Global cooling?
Past evidence suggests there may be a correlation between sunspot activity and global temperature.

A seventy-year cold snap in the seventeenth century, which saw the River Thames freeze over, coincided with a drop in sunspot activity known as the 'Maunder minimum'.

While the link seems to be supported by other geological evidence, Oughton says that it is only speculation.

He says no mechanism has been found which would prove a connection between minimal sunspot activity and cooler temperatures.

Oughton says the most exciting thing about this unusually quiet period is that it gives scientists like the opportunity to gather more data and fine-tune their predictions.

But if it continues, "it could be interesting," he says.