Scientists predict that the sun’s magnetic field is about to flip, according to a NASA Science article. The celestial event may mark the midpoint of the current solar cycle 24.

“It looks like we’re no more than 3 to 4 months away from a complete field reversal,” the article quotes solar physicist Todd Hoeksema, the director of Stanford University’s Wilcox Solar Observatory. “This change will have ripple effects throughout the solar system.” As the article explains, the sun’s magnetic field switches polarity approximately every 11 years at the peak of each solar cycle. The pending reversal means we’re halfway through the current cycle.

Wilcox is one of the world’s only observatories that monitor the sun’s polar magnetic fields. NASA says that since 1976 magnetograms at Wilcox have recorded three “grand reversals” — with a fourth in the offing.

Solar physicist Phil Scherrer, also of Stanford, explains it this way: 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.” The effect of the change in the heliosphere are felt all the way out to the edges of interstellar space. The flip also affects cosmic rays, which pose a danger to astronauts and space probes, and, according to some researchers, may affect Earth’s cloud cover and climate.

“The sun’s north pole has already changed sign, while the south pole is racing to catch up,” says Scherrer. “Soon, however, both poles will be reversed, and the second half of solar max will be underway.”

Twin Peaks

A ScienceCasts video, “Solar Max Double Peaked,” linked from the article, quotes Dean Pesnell of the Goddard Space Flight Center as predicting a double peak to cycle 24. Pesnell was a member of NASA’s Solar Cycle Prediction Panel, that gathered in 2006 and 2008, when solar activity was at a minimum.

Pesnell believes that cycle 24, which saw peak sunspot numbers in 2011 followed by a dip in 2012, could rebound later this year and into 2014 — possibly 2015. As the video points out, solar cycles are not as regular as we may have been led to believe, with lengths varying from 10 to 13 years, and solar maxima are not regular either. The Solar Cycle Prediction Panel had predicted cycle 24 to be a below average cycle, with a sunspot maximum of 90.

The last two solar cycles, with peaks around 1989 and 2001, respectively, each had two peaks, with the second “mini-cycle” lasting about 2 years each time. Pesnell believes history could be repeating itself.