Crumb Trail
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Monday, March 06, 2006

We tend to think of our star, old Sol, as being a constant in our lives, just as day follows night. But the sun is no more stable than the earth. It has an atmosphere, sort of, and storms so intense that we have nothing comparable to allow analagous understanding. The solar weathermen are predicting heavy weather.

The next sunspot cycle will be 30-50% stronger than the last one and begin as much as a year late, according to a breakthrough forecast using a computer model of solar dynamics developed by scientists at the National Center for Atmospheric Research (NCAR). Predicting the Sun's cycles accurately, years in advance, will help societies plan for active bouts of solar storms, which can slow satellite orbits, disrupt communications, and bring down power systems.

The scientists have confidence in the forecast because, in a series of test runs, the newly developed model simulated the strength of the past eight solar cycles with more than 98% accuracy. The forecasts are generated, in part, by tracking the subsurface movements of the sunspot remnants of the previous two solar cycles. The team is publishing its forecast in the current issue of Geophysical Research Letters. . .

The Sun goes through approximately 11-year cycles, from peak storm activity to quiet and back again. Solar scientists have tracked them for some time without being able to predict their relative intensity or timing.

Forecasting the cycle may help society anticipate solar storms, which can disrupt communications and power systems and affect the orbits of satellites. The storms are linked to twisted magnetic fields in the Sun that suddenly snap and release tremendous amounts of energy. They tend to occur near dark regions of concentrated magnetic fields, known as sunspots.

Solar storms affect earth weather too. They make the sun hotter and over the last 100 years have made a contribution to earth temperatures estimated to be between 4% and 20%. They affect climate in more subtle ways too. Sol also has a magnetosphere which affects the whole planetary system. It shields the system as a whole from cosmic rays and interacts with other magnetospheres, such as that of the earth. Sol's polarity reverses in an eleven year cycle, much faster than Earth, and magnetic storms - sun spots - fluctuate in number and intensity during the cycle. The effectiveness of Sol's field as a shield depends on polarity, a combined effect of polarity and direction of rotation. Sol is both a source and a shield of cosmic rays. There has been recent research on how cosmic rays affect climate. They create high level clouds which alter planetary albedo, reflecting more of Sol's energy and cooling the planet. So, the sun will be hotter but increased cosmic ray bombardment will create high level clouds that reflect more light. The relative intensity of these effects isn't clear.

Other researchers looking at solar cycles for the past 11,000 years have predicted that the the next 100 years will be less stormy than the past 100 years. Good. We could use a little solar dimming while we get our atmosphere spruced up a bit. This comming storm may not repeat again for quite a while.

posted by back40 | 3/06/2006 02:04:00 PM


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