Monday, August 22, 2022

Cycles Upon Cycles

Regular readers know that I frequently post on the solar activity cycles, and have been doing so for most of the life of the blog.  This is largely because I find it interesting - solar activity has an enormous impact on my ham radio hobby, and there's plenty of evidence that solar activity affects the earth in ways besides the "10.7 Centimeter Solar Flux Index (SFI)" that hams obsessively track.  About that radio propagation; the 10.7 cm (2803.738 MHz) is incapable of affecting the ionosphere and causing the improved propagation we associate with the higher solar flux.  That wavelength simply doesn't have enough energy.  What affects the ionosphere is the flow of charged particles from the sun - that is, ions hitting or interacting with the ions in the ionosphere.   

This display of solar terrestrial data is found all over the web, from N0NBH.  The 10.7cm Solar Flux Index (SFI) is top left.

Everyone who gets near this subject learns that solar activity goes through an average 11 year cycle of activity.  Increasingly, though, it seems to be emerging that there are cycles within that cycle.  Space News is reporting that a new observation is pointing to a shorter cycle (or sub-cycle) found within the longer cycle that is better at predicting solar flares and the potentially hazardous solar activity.

Partnership for Heliophysics and Space Environment Research (PHaSER) scientist, Robert Leamon, the new framework is based on research that indicates notable and sometimes abrupt changes in the solar cycle occur with a rhythm at each one-fifth of a cycle.

Taking a cue from musicians (I suspect), Leamon and the team refer to this as the cycle of fifths.  The team is saying that despite the fact solar cycles can vary by months or even years, they still operate with a clear and predictable sequence of events.  Consequently, if they observe the things they expect for a certain fifth of the cycle they can say that's where we are in the cycle. This is reminiscent of how researcher Scott McIntosh, whom I've referred to many times, observes visible effects in the sun's surface seen in the right wavelength of light and declares a termination event that puts a line between the old and new solar cycles.  Dr. McIntosh is a co-author on the paper.  

At two-fifths of a cycle dark regions known as polar corona holes formed at the sun's poles. At the three-fifths mark, the sun blasted out that cycle's last X-class flare ,  a strong and potentially hazardous type of solar flare.

Less consistently, at four-fifths of a cycle, sunspots at the sun's photosphere reach a minimum. Then the final event of the cycle the sun passes through another terminator. 

"The max number of sunspots doesn't quite align with when the polar field reverses, but the polar field reversal happens at exactly one-fifth of the cycle going from terminator to terminator," Leamon said.

With a young theory like this, unless they've been able to compare predictions to records going back more than just this cycle and the last, I'll have to say it's interesting, but I'm most interested in its prediction power.  I'll judge it based on how good is it at telling us the likelihood of flares and Coronal Mass Ejections (CMEs) is going up.  

The second cycle upon cycles is that within a cycle, the number of flares and CMEs is not smoothly increasing to the peak and then smoothly decreasing.  Let me grab a graphic from a few weeks ago:

Sunspot cycle progression from the Spaceweather Prediction Center.

Now let me zoom in on the start of cycle 25 in a bit more detail. Note this one as one more dot on the right end of the measured data.  This is from a month newer chart on their website.

The dots along the purple "measured data" curve are the sunspot number measured plotted on a monthly basis, and while I can't find higher resolution, there's an observation going around that there's a subcycle that this data just hints at.  It's said to be on the order 11 or 12 weeks, and while I've tended to write that off to coincidence, I have noticed that sunspot numbers were bigger in mid-June and mid-August than mid-July.  There were more CMEs and some m-class flares a week ago and the solar activity has been dropping since then.  I have to say, though, that my ability to see that depends too much on when I can spend long periods in the ham shack.  I can easily accept I may be wrong and the other guys who talk about it have a better handle on it than I do.  

Food for thought.


  1. Try some of these sites these:


    1. Egg-zactly. I tend to watch his morning videos every day although I miss a few, and I have a bookmark for space weather news. There's data there I don't see elsewhere.

      Ben Davidson is the guy whose shorter cycles I was trying to find references to and couldn't.

  2. A simple FFT analysis should identify all the cycles embedded in the data.

    1. People have been doing that since FFTs were invented. We've had some who were sure that this cycle would be lower than others, leading to a minimum in the next cycle (call it the 2030s). Probably the best known of the group is Dr. Valentina Zharkova. She was one of the few that correctly predicted solar cycle 24 would be weaker than cycle 23 - only 2 out of 150 models predicted correctly - and she was saying we're entering the next grand minimum. Then Scott McIntosh came along with a different approach and said this cycle would be stronger. At one point, he was predicting an extremely strong cycle, but as time went by and the predicted termination of cycle 24 didn't happen when expected he revised his forecasts down.

      I think most of the work to date has been various ways to impose an FFT on the data. Zharkova's work is based on FFTs of the magnetic cycle, but only for a short time. The weak part is that while it's a smart, modern technique, it still depends on observations from a short period of time. While it matches these observations well, I question how well it can be extrapolated over thousands of years.