The Sun’s magnetic field changes polarity approximately every 11 years. It happens at the peak of each solar cycle as the Sun’s inner magnetic dynamo re-organises itself.
The reversal will mark the midpoint of Solar Cycle 24. Half of “solar max” will be behind us, with half yet to come.
“It looks like we’re no more than three to four months away from a complete field reversal. This change will have ripple effects throughout the solar system,” said solar physicist Todd Hoeksema of Stanford University.
Magnetograms at Wilcox have been tracking the Sun’s polar magnetism since 1976, and they have recorded three grand reversals — with a fourth in the offing. “The Sun’s polar magnetic fields weaken, go to zero and then emerge again with the opposite polarity. This is a regular part of the solar cycle,” Solar physicist Phil Scherrer, also at Stanford, said.
A reversal of the Sun’s magnetic field is, literally, a big event. The domain of the sun’s magnetic influence (also known as the “heliosphere”) extends billions of kilometres beyond Pluto. Changes to the field’s polarity ripple all the way out to the Voyager probes, on the doorstep of interstellar space. When solar physicists talk about solar field reversals, their conversation often centres on the “current sheet.” The current sheet is a sprawling surface jutting outward from the Sun’s equator where the Sun is slowly rotating magnetic field induces an electrical current. The current itself is small, only one ten-billionth of an amp per square meter, but there’s a lot of it: the amperage flows through a region 10,000 km thick and billions of kilometres wide. Electrically speaking, the entire heliosphere is organised around this enormous sheet, researchers said. During field reversals, the current sheet becomes very wavy.
Source: http://tinyurl.com/mbwu5nd
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