In this convection zone, roughly the Sun's outer third, different regions rotate at different rates. A spot painted on the equator, for instance, would go around in about 25 days, but near the poles a similar spot would take 33 days to fully rotate. "We're keenly interested in this," Toomre says, "because we think it ties in very closely with how stars like the Sun build and rebuild their magnetic fields. For instance, we know the Sun has 11-year cycles during which the polarity of the north and south poles changes. Is the building and rebuilding of magnetic fields taking place in the highly turbulent region? These are some of the big physics questions of the past few decades, and we need to understand them if we are going to have some comfort in predicting the Sun's cycles and variability."
While the Earth has gone through many ice ages, notes Toomre, their causes aren't well understood. "Is it because the planetary orbits have been jiggled, or is it partly because the heat flow from the Sun has changed? It also could be caused by particle flows from the Sun. Then the issues of rotation stability and magnetic action become important."
go back to the main screen