Wednesday, April 22, 2020

Solar Cycle Update - We Seem to Have Begun Cycle 25

Long time readers will recall that I used to do a “Solar Update” roughly every six months, but it seems my last regular update was in April of '18.  I kind of got out of the habit when the news every month was roughly the same: we're in an extended minimum.  I did a post on keeping an eye on the solar minimum last December when we were about to set a record for the longest stretch of days without a sunspot - and did a couple of days after that post.
UPDATE: Dec 16 1630 EST:  The record was broken Sunday.  From
SUNSPOTS BREAK A SPACE AGE RECORD: Solar Minimum is becoming very deep indeed. Over the weekend, the sun set a Space Age record for spotlessness. So far in 2019, the sun has been without sunspots for more than 270 days, including the last 33 days in a row. Since the Space Age began, no other year has had this many blank suns.
In the last few months, there has been talk among the ham radio propagation watchers that the majority of sunspots since then - around Christmas of '19 - have been new solar cycle spots and that the week around Christmas to New Year's of '20 might end up marking the start of cycle 25.  (New cycle spots are instantly recognizable because they're closer to poles than the solar equator and they have reversed magnetic polarity from those closer to the equator.)

Today we find an article posted on Watts Up With That saying Cycle 25 has just started.  In saying so, the rely on an arcane measurement called the heliospheric current sheet tilt angle, and show that the angle has flattened recently, and they mark the similar points in the previous cycles.

They state that much like “it ain't over until the fat lady sings” ...
The solar cycle isn’t over until the heliospheric current sheet has flattened. The data is provided by the Wilcox Solar Observatory at Stanford University. There were no observations from about 19 December to 5 February; so the values in between have been interpolated from the rotations before and after.
By two measurements; the number of rotations of the sun, (a Carrington rotation or solar day is 27.23 earth days) and by measurements of the 10.7 cm solar flux, they conclude the length of cycle 24 was 11.1 years, which is the average solar cycle length.  Cycle 23 was an outlier with a very extended minimum but this one was average. 

I find it interesting that the planetary A index, a measurement of geomagnetic activity, for cycle 24 continues the trend of being lower than the 20th century “modern warm period.”  This plot shows that from 1932 until 2009 this geomagnetic index never went below values that were on the high side for cycle 24.  I think anyone older than about four could look at this plot and play “one of these things is not like the others.”

A coincidence in timing to be sure, but the ARRL reports that NOAA released their predictions for Cycle 25 and stick with their previous predictions of another cycle like the last one.  
“While this is SWPC’s official Cycle 25 prediction, it’s important to note there is still divergence among various forecasting methods and members of the space weather forecasting community,” Donovan said. “Most forecasts and forecasters agree that the Cycle 25 is likely to be within ±20% of Cycle 24 and is likely to occur between 2024 and 2027.”
To the best of my knowledge, Dr. Valentina Zharkova is still predicting that Cycle 25 will be weaker than the last and that there may be an extended minimum lasting until potentially as late as 2053.  Ish.


  1. Break it down for me. I know what many are saying about the extended solar minimum but where is the science? What does it really mean? Or are we in uncharted (sure there IS a chart, but you know what I mean) territory?

    1. New cycle spots appear in a different place than older cycle spots.

      That's a vague recollection from a decades ago Astronomy class.

    2. Predicting the next solar cycle has gotten past the reading tea leaves stage. Everyone is trying to predict based on magnetic measurements and space-based sensors for UV and solar wind. Dr. Zhakarov's method was to characterize the changes over time in the solar dynamo (magnetic field changes, which alternate north/south every solar cycle) and do a Fourier analysis to generate functions describing the changes vs. time, then plot it backward and forward in time. She started out with two principle components and got good agreement with the record as far as we have data. Things like the Maunder minimum, the little ice age and the modern maximum were easily seen. Then she refined the model to four principle components.

      Using this method, hers was one of only two models that correctly predicted solar cycle 24 would be weaker than cycle 23 - two out of 150 models. Her models say that events like the little ice age occur on regular cycles of about 350-400 years, and that cycle 26 (roughly 2031 through 2042?) will be the end of the "modern maximum." After 2050 the sun goes back to more like 20th century levels so if we have a little ice age it won't be as long as the last one. I hope to live long enough to see that.

      As with all science, if it doesn't accurately predict it's not worth much.

      Unlike, say, climate scientists, she puts her algorithms and data out front for serious peer review. She says emphatically and repeatedly that she's not a climate scientist, she's a solar physicist. Which is like saying, "I'm not a climate scientist, I'm a real scientist."

  2. SiG follows this closer than I do these days, but there are definite, quantifiable signs of when a new cycle starts. Predictions of future activity are still pretty much a chicken bone toss AFAIC, but since the new cycle has started we can look back and compare the duration of this minimum to previous ones, and simple arithmetic gives the number of days. I haven't looked closely to see how this recently ended minimum compares to others. If no "new" spots had appeared, then we might be entering uncharted territory.

    I'm sure Sig can state this better than I can.....

  3. I get emails from the space weather blog and they said a new cycle started a couple of months ago and confirmed it by the polarity change.