Earth at Aphelion

StarDate: July 1, 2009

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As we head into the long, hot days of summer, we can be grateful for one thing -- the Sun is farthest from us at this time of year. In fact, we'll reach our maximum distance from the Sun this week -- about three million miles farther than when we were closest back in January.

Because we're farther away, we receive less energy from the Sun. And that's on top of the fact that over the last year, the Sun has actually emitted less energy than average.

The Sun is at the "bottom" of its 11-year magnetic cycle -- a time known as solar minimum. There are fewer sunspots at solar minimum, and fewer outbursts of particles and energy.

But this has been the quietest solar minimum in almost a century. Last year, the Sun showed no sunspots at all for about two-thirds of the time. And sunspots were even scarcer for the first three months of this year.

The calm has had several other effects. The solar wind has been slower and thinner than average, for example, and the Sun's total energy output is down.

No one's quite sure why the Sun is so quiet, because the details of its magnetic cycle are poorly understood. So no one can be sure what will happen at the next solar maximum -- the time when the number of sunspots reaches its peak. It, too, could be quiet -- or this lull could be the calm before the storm. About all we know for sure is that the Sun will reach solar maximum in three or four years.

More about the solar cycle tomorrow.

Script by Damond Benningfield, Copyright 2009

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