Sunday, May 19, 2024

Solar Cycle 25 Update for Mid-2024

While talking about the geomagnetic storms and some extrapolation about the solar cycle yesterday, it occurred to be that I hadn’t done one of my (semi-? fairly-?) regular update posts on Cycle 25 since mid-December, so six months between them seems like a good time to do another.  

Like the last time, Dr. Scott McIntosh of the National Center for Atmospheric Research, NCAR, gave a solar cycle 25 update on a radio group that I follow, about a month ago, and this is going to be based on what he talked about. I’m going to lead with NOAA Solar Cycle Progression chart from their web site as I often do. 

The gray band is the expected range of the sunspot number, the black trace showing a lot of peak to peak variation is the measured sunspot number, which has been higher than predicted for virtually all of the cycle. 

This horizontal scale is more spread out horizontally than the plot I used in December so that I could put a marker (red vertical line) at the last point for the monthly smoothed sunspot number (SSN) at the right end of the previous plot. You can easily see that the SSN hasn’t achieved the values from 2023. In the last month, we achieved the highest sunspot numbers since cycle 23, but two things apply here. First, this doesn’t include the month of May, and second, a monthly SSN isn’t necessarily moved by a couple of large daily numbers, it’s more like an average. We saw days with sunspot numbers into the 240s. 

Dr. McIntosh of NCAR is tremendously interested in the Smoothed number because it’s an indicator of the cycle’s strength. He rather famously predicted that cycle 25 would be much stronger than average, and rival some of the strongest ever. While his methods for predicting the end of one cycle and start of the next are new, he missed his prediction for the end of cycle 24 by about a year with the termination event showing up in December of 2021. That, in turn, lowered his predictions for cycle 25. While his predictions for the cycle match reality better than the majority of predictions before 25 really started, the cycle is turning out rather average.

This next graphic is kind of dense to look at – it combines two of Dr. McIntosh’s plots showing the previous cycles back to 1975 with his prediction from 2020 (in red) at the right end. Pasted to the right of that is the part of a duplicate plot that shows how it has actually developed. Note how the actual measured data is approaching the red, 2021 prediction and the green Mean Solar Cycle since 1750.

Finally, a plot I’ve shown regularly which shows the SSN for the last five cycles back to 1975. I like this plot because it’s my ham radio biography in one plot. I was first licensed in February 1976, so every cycle I’ve been through is on this plot (and I was a shortwave listener for the cycle before that). The plot is posted to Space Weather News, but is created by a separate site,

Which brings us to the big questions. So what happens next?  I’ll answer with one of my favorite quotes, this time from physicist Niels Bohr: "Prediction is very difficult. Especially if it's about the future." More seriously, will this cycle be a cycle with dual peaks like pretty much all of them on this plot have been? My guess is yes, it will be like the majority of these; mostly flat for a couple of years with a couple of peaks. Cycle 22 (black) appears to be flat for around 30 months or 2-1/2 years. Cycle 23 (red) has a more pronounced double hump but is above that dip between them for more like 40 months or 3-1/2 years. Cycle 24 (pink) the weakest cycle in 100 years held a Smoothed Sunspot Number above its dip between the peaks for close to 48 months. 

Dual peaks might be an indication of asymmetry between the northern and southern hemispheres on the sun; the dual peaks might become a stronger single peak if the two hemispheres had the most effective sunspots at the same time in close to the same numbers.

What Dr. McIntosh seems to be most interested in answering in that presentation is when cycle 26 begins and 25 ends.  His method of predicting the strength of the cycles depends on the start. He expects to see the first signs of cycle 26 starting before the end of this year.

Getting back to the dual peaks, cycle 23 was spitting CMEs and flares for a lot of time. The short green to olive drab curve between cycles 23 and 24 is this one, 25, and we’re not quite four years into what is generally thought of as an 11 year cycle. Put another way we’re 45 months into a roughly 132 month cycle. The past month got a lot of attention for the flares and CMEs that are more prevalent through the peak years and the first years of the decline to the cycle’s completion. It seems like an easy prediction to say we’ll be seeing more CMEs, solar flares and geomagnetic storms for the next four to five years.


  1. Guy upstairs is giving the world a super suntan. The sun feels very strong lately lot more intensity it seems. Have had to skip working the garden during mid day its so strong. I know its not my imagination, this year so far is quite stringer than any I remember. Don't know if thats attributable to the extra activity of this sun cycle though. It is simply too much for me this year.

    1. You know, I'm not aware of a single piece of measured data that backs that. Millions of people have solar panels. If they were getting more power per square yard of panels, you'd think they'd notice. Not just the industrial or government monitors, ordinary people. The solar cycle isn't remarkable in any way related to hot it feels or how strong the sun feels. The data up in the post shows it's almost as good as the average cycle as long as we've been measuring them.

      I haven't worked in our yard or flower beds between about 10AM and 2PM in years - decades, I think. This is Florida and one of our rules of life is that Nature Wants You Dead, whether it's the sun, the Burmese Pythons or just about everything else.

      Are you familiar with the old principle of science called Occam's Razor? When you're comparing explanations for something you're trying to understand, the simplest explanation is probably the right one? The simplest explanation here is that the sun feels stronger to you this year than last year because you're one year older.

    2. Could be, there's many possibilities. I just know what I experience as you point out. Yeah, working the garden, has that certain Zen to it. Great self therapy. Down to a solid 4 hours a day working on projects and garden, plus a couple hours in the shop evenings, got a number of R&D projects, like a 44 mag auto pistol, very low bore axis, its a long recoiling barrel system, shoots low power 44 special so far, not up to full power 44's, need to wind some piano wire springs for that, I'm a 44mag fan thru and thru, so when thats finished, have a really trim handy auto carbine design want to attempt.

      Don't have any dedicated data logging on the off grid system, certainly plenty of good sun keeping the battery charged. No complaints there. Some years though, have had loooong stretches of low/no wind and cloudy weather, had to break out the gas drive charger, its an old single port beetle-bug engine, runs about 800rpm, pulleyed up the belt ratio driving a PMA alternator and a 1 wire AC Delco style racing alternator jegs sells to the circle track racers, 400 and 100 amps respectively, the 400amp PMA puts out serious juice, has to be spun very quickly to keep adequate cooling air thru the windings, its used if the battery needs more than 20% charge, its a beast, otherwise the 1 wire alt works excellent, and the Vdub engine sips fuel like the best gas drive imaginable, real miser, makes more torque than needed at 800rpms, max amps output, using 780 watts to the horsepower formula.
      Use a precision gravity meter and watch the at rest voltage, after equalization charge, monthly, carefully when its night and the turbine off charge into dump mode/no battery in the circuit and is only heating the preheat hot water tank, using a small 7amp-hour motorcycle battery as a buffer/capacitor when the wind power PMA's are direct feed to the cluster of 12vdc resistance water heater elements, so all's i got, its real time analog data logging, lol's. I'm no Silicon Graybeard thats for sure, more of a wing it graybeard, with creativity and trial and error, combined with some common sense, (i hope!),
      Next a roof water cistern, for our location we receive ave 48inches rain yearly, twice whats needed to replenish a 2400 gal cement block cistern three times. That be close to fifty a month we retain, after payoff, last estimate materials was $1800, so not many month payback. Its all a kind of holistic thing.
      Mains bill dropped $20 bucks more last month compared to last month and same month a year ago, (used 265KWhrs less than last year same time). Course weather effects those numbers too depending on how cloudy it is. Lot of folks I read get real deep into every erg of power possible on their systems, can understand particularly for folks who contract a total install for either grid feed or off grid, lot more expense than doing a DYI system. We built it by purchasing components and bits by the monthly cash on the barrel head system. In the larger scope, steadily been able to decrease our outgo funds, and the system payed itself back fully, so in effect its all gravy and details like exact power production are not all that important, its worry free, long as the battery is fully charged its all good.
      Hey, if your into DC to AC inverters, been running AIMs Power units, excellent quality, first inverters been running non stop for 10 or 11 years, just hums along. Went semi sine wave over pure sine wave, no issues at all. They run everything so far, though the fridge makes some strange noises verses regular mains power on the inverters, though we use a 12vdc TV to watch dvds. Gave up media TV many moons ago.
      Appreciate your insights. Don't have the engineering/math technical mind like yours, mines more of a got ideas go for it style with lots of broad scope welding/fitter-fab/mechanical experience to back me up. Different strokes.

  2. And, in many urban environments, there are fewer trees and more pavements.
    In SC, which is both hot and un-Godly muggy, my house was - almost all of the time - bearable, due to the MANY trees on my property. It was so shady and damp, that every time it rained, I had a veritable field of mushrooms (BIG ones) pop up overnight.
    I cannot tell you how much I appreciate the solar and sunspot updates - I'm also a ham, and just now really getting into contacting, after a multi-year absence. I just returned from Hamvention, and I'm putting my money into smaller, low-power radios and computers/tablets.
    I also attended a forum on setting up Winlink - these days, you never know when the internet might get interrupted, whether via normal power outages, deliberate activity, or - I hope not - unofficial action by a government incensed by free exchange of information. The ability to bypass monitored and sanctioned messaging may at some point, be critical. Even if a CME would disrupt much of the available infrastructure, a radio to radio messaging system could be invaluable.
    Plus, it's a hoot to show people - especially kids - just how it can be done WITHOUT cell phones/Internet.

    1. I've got a friend who's in to Winlink and a lot of that "new fangled" stuff. I've asked him to do a guest post on it but he hasn't been forthcoming.

      Radio to radio messaging related. A CME collapsing the power grid or an EMP from some foreign maniac are both exceedingly unlikely. Even that though, is unlikely to affect your radios. I did a pretty deep dive on this in the early days of the blog, and I don't mean to just say, "go read these old posts" but if you want to, they're here.

      The majority of the energy in an EMP is in low frequencies. For example, if you have a full-size 20 meter dipole with the "textbook EMP", you get less than one milliwatt. That's not going to damage any receiver anywhere. At 2 meters, it's 1/10 of that.

      And CMEs are even weaker than that. As McThag pointed out on his blog, with all the talk about this last (May 10th) storm from a CME being one of the strongest of all time, it pretty much negates the talk of another "Carrington event" CME taking out the planet. Didn't happen.

      If it makes you feel better, put your emergency radio in a metal ammo box, but simply disconnecting the antenna and power supply wires is where the benefit comes from. This stuff isn't magic, it's just plain radio.


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