The Sun's Magnetic Field is Flipping

Perhaps you've heard about it with some anxious comments that the sun's magnetic field is undergoing a reversal. These magnetic field reversals occur near the peak of every solar cycle, and have happened approximately every 11 years for all of human history and all of Earth's history. 

Dr. Scott McIntosh, of the National Center for Atmospheric Research (NCAR) was given a hint by a mentor when he started studying the sun there. For years, it was known there were spots on the sun that were bright in the Extreme Ultra Violet spectrum. His mentor, Dr. Gurman, said to find and track those spots, adding, "you might find something interesting." That led to the best prediction of this solar cycle that was published before cycle 25 really got started. His predictions for our current cycle were based on the prediction for the magnetic field (Hale cycle) flipping sooner than it really did which is why he predicted it being stronger than it has been. He's rather interested in predicting when this cycle is going to end and the beginning of cycle 26 is going to be seen.

The pattern, analyzed over the preceding cycles looks like this:

Screen capture from one of his regular videos for the Front Range 6 Meter Group on groups. io. 

The alternating patterns of colors converging toward the middle, then changing to the opposite color is as prominent as can be. (Call whichever color you like magnetic north or south). When both the red and blue diagonal lines converge at the equator, that's the Termination Event for the cycle. The red and blue areas are plotted with the year on the horizontal axis and latitude on the sun on the vertical. The solar equator, latitude zero, is the middle line. The other two horizontal lines are +/- 60 degrees. The complete cycle, called the Hale Cycle is two sunspot cycles, or averaging 22 years. 

The green plot above the magnetic plot is the smoothed sunspot number and the date goes from 1945 on the left to 2025 on the right. The second green curve from the left is cycle 19, the most active cycle ever observed. The second from the right is the previous cycle, 24, the weakest in a hundred years.

There's a lot that can be learned just from this one screen capture from Scott's March presentation. Note in particular that the dashed lines between termination events are not equally spaced. Cycle 23 (2nd from the right) is wider - longer - than 24 and much longer than 22 that preceded it. The second lowest cycle, the one right after cycle 19 (third from left) lasts longer than the one after it. These convergences toward the equator are mirrored in the sunspot distribution. As the cycle starts, the spots are higher up on the disk, and as it progresses, they show up progressively lower in latitude.

(Image credit: Future)

Another thing you might conclude from the image is that the field doesn't just suddenly flip. Those sloped lines are years long. In fact, looking at the red and blue lines, it's probably better to not think of it as flipping, but as constantly changing.

To those trying to scare you about this, at roughly 11 years per flip it's not a short term effect, but in the big picture it happens regularly often enough so that with a modicum of luck we all get to live through several of these field flips.