NASA: Sun Getting Ready For A 'Field Flip' : The Two-Way Scientists say the sun will reverse polarity within the next three to four months in an event that marks the midpoint of "solar max" — a period of peak solar activity.

NASA: Sun Getting Ready For A 'Field Flip'

Our nearest star is about to pull a once-in-11-years move by swapping its north and south magnetic poles.

The sun's polarity switch is a natural part of "solar max" — the period of peak activity during what averages out to be roughly an 11-year cycle. According to NASA, this year will mark the fourth time since 1976 that scientists have observed the 180-degree pole flip.

"It looks like we're no more than 3 to 4 months away from a complete field reversal," solar physicist Todd Hoeksema of Stanford University says on NASA's website. "This change will have ripple effects throughout the solar system."

The reversal marks the midway point of solar max, but it's a gradual process, says Phil Scherrer, another Stanford-based solar physicist.

"The sun's polar magnetic fields weaken, go to zero and then emerge again with the opposite polarity," he says.

While those ripple effects will go largely unnoticed on Earth, they will affect the size and shape of the undulating magnetic envelope that surrounds the solar system out to a boundary with interstellar space known as the heliopause. (The Voyager probes, launched in 1977, are hovering near that boundary now.)

Just before the switch, the magnetic field becomes very wavy, and as the Earth passes through it, it's likely to "stir up stormy space weather around our planet," NASA says.

"The sun's north pole has already changed sign, while the south pole is racing to catch up," Scherrer writes. "Soon, however, both poles will be reversed, and the second half of Solar Max will be underway."