Reversed Polarity

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When a character in TV science fiction faces a tough technical problem, one solution always seems to work: reverse the polarity.

That may not fix problems in real life, but for the scientists who study the Sun, reversing the polarity is a big event. It signals that the Sun has started a new 11-year cycle of magnetic activity.

A new cycle began in January, when telescopes on the ground and in orbit measured a small sunspot -- a relatively cool, dark magnetic "storm" on the surface of the Sun. The observations showed that the polarity of the sunspot was reversed from that of the sunspot before it.

As the Sun spins on its axis, different layers of hot gas spin at different rates. That generates a powerful magnetic field around the Sun.

Over a period of several years, the lines of magnetic force get twisted and tangled. That produces many more sunspots. The lines can also cross each other, creating "short circuits" -- powerful explosions of energy and particles. These outbursts can disrupt communications and electrical systems on Earth.

At the end of a cycle, the Sun's magnetic field flips over: magnetic north becomes magnetic south, and vice versa.

The Sun has been quiet for the last few years. But the start of a new cycle means that it'll get busier in the years ahead. The new cycle should peak around 2012, and end around 2019 -- when scientists will once again be waiting for the Sun to reverse polarity.

More about the Sun tomorrow.

Script by Damond Benningfield, Copyright 2008

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