The Solar Radio Microwave Flux

UPDATE: The SWPC press conference audio is now available, hear it here

Shortly after SWPC dropped on their website their still invisible “press conference” ( I have yet to get the link to audio, even though requested twice from Doug Biesecker) Leif Svalgaard remarked that the 10.7 cm radio flux graph produced by SWPC in that announcement on their web page was “just wrong”.

SWPC_radioflux_Apr09

After spending months as a regular supporting commenter, Leif asked if he could write a guest post about it. After several microseconds of uncertainty, I said “yes”. So for the first time ever on WUWT, I present Dr. Leif Svalgaard as guest author, rather than commenter. – Anthony


The Solar Radio Microwave Flux

Guest Post by Leif Svalgaard, May 2009

(A PDF of this essay is available here)

Since 1947 we have routinely measured the flux of microwaves from the Sun at wavelengths between 3 and 30 cm [frequencies between 10 and 1 GHz]. This emission comes from high in the Chromosphere and low in the Corona and has two different sources [although there is debate about their relative importance]: thermal bremsstrahlung [due to electrons radiating when changing direction by being deflected by other charged particles] and ‘gyro’-radiation [due to electrons radiating when changing direction by gyrating around magnetic field lines]. These mechanisms give rise to enhanced radiation when the temperature, density, and magnetic field are enhanced, so the microwave radiation is a good ‘measure’ of ‘general’ solar activity. As strong magnetic fields are located in specific regions that can live for weeks and often reoccur at or near the same location for months [perhaps even years], there is a strong rotational signal in the emission superposed on a solar cycle variation of a ‘background’ activity level. At solar minimum, especially a ‘deep’ one as we now experiencing, the effect of active regions largely disappears and we observe a sort of solar ‘ground state’.

As the radio flux measurements [as opposed to the sunspot number] are unaffected by changes of [human] observers and their observing techniques and instrumental and atmospheric differences they may be a ‘truer’ and more objective measure of solar activity [to the extent that we can reduce this complex concept to a single number per day] and the many decades-long flux record could throw light on the important issue of the long-term variation of solar activity. The solar microwave flux is nominally an absolute flux, one solar flux unit defined as [the very small amount of] 10-22 Watt per square meter per Hertz. Making an absolute measurement is always difficult and considerable uncertainty and debate surrounded these measurements early on, before being settled by international cooperative work in the late 1960s [Tanaka et al., Solar Phys. 29 (1973) p. 243-262; http://www.leif.org/research/Tanaka-Calibration-F107.pdf]. By observing the radio flux from supernova remnants [Cassiopeia-A, Cygnus-A, and Virgo-A] one can verify the constancy of the calibration.

The longest running series of observations is that of the 10.7 cm [2800 MHz] flux [often simply referred to as ‘F10.7’] started by Covington in Ottawa, Canada in April 1947 and maintained to this day[and hopefully much longer] at Penticton site in British Columbia [http://www.hia-iha.nrc-cnrc.gc.ca/drao/solar_e.html]. The data is available from several sources, e.g. from the NGDC at http://www.ngdc.noaa.gov/stp/SOLAR/FLUX/flux.html, more timely at ftp://ftp.geolab.nrcan.gc.ca/data/solar_flux/daily_flux_values/current.txt. There are three measurements per day with small systematic [and poorly understood] differences. One can either average all three, or as in this work only use the noon value [for Penticton at 20:00 UT, since 1991].

As with all solar indices, there is the issue of the varying distance between the Earth and the Sun. For describing the effect on the Earth’s atmosphere and environment the proper values of the indices to use should, of course, be the ones observed at the Earth, but for studying the Sun, those values must be adjusted to the mean distance [at 1 astronomical unit]. This is not always appreciated and one sees endless discussions about F10.7 changes or flat-lining without the 7% change caused by the varying distance being taken into account. Needless to say, here we use the ‘adjusted flux’.

So, what does the record look like? Figure 1 shows the entire record up to date of writing [14 May, 2009], plotting the ~23,000 daily noon values [pink curve] and a running 27-day mean [black curve]:

svalgaard_radioflux_fig1

The solar cycle variation is obvious, but so is another fact: [highlighted by the green box] that the flux at every minimum is very nearly the same. There has been no clear systematic variation or trend in the ‘ground state’. Figure 2 shows the 1954 minimum overlaid the current minimum, and is a rather dramatic demonstration of the constancy of the ground state (also shows nicely the 27-day recurrence tendency):

svalgaard_radioflux_fig2

Other observatories have long and continuing series of measurements of the microwave flux. Of note is the long series from Japan (Toyokawa 1951 Nov – 1994 Apr; Nobeyama 1994 May – present) at several wavelengths around the 10.7 cm (e.g. 3.75 GHz = 8 cm; 2 GHz = 15 cm; and 1 GHz = 30 cm). The fluxes at these wavelengths are highly correlated with each other. Figure 3 shows the correlation of 3.75 GHz versus 2 GHz:

svalgaard_radioflux_fig3

This means that we can use the regression equations to put all the measurements on the same scale, scaling [marked with an asterisk] them to 3.75 GHz (Figure 4):

svalgaard_radioflux_fig4

This looks very much like Figure 1 [the coefficient of determination of the correlation with F10.7 is as high as R2 = 0.987, which is a welcome finding as one observatory series then supports the other, at least to the accuracy of the scatter plot]. Scaling the average of the Japanese [scaled] observations to F10.7 we obtain (Figure 5):

svalgaard_radioflux_fig5

If you look very closely, you might see that the red curve (Japanese stations) lies a little bit below the green curve (Canadian stations) before 1991 and a little bit above the green curve thereafter. Here is a plot of the ratio of the flux values of the two series (Figure 6) with different colored symbol for the Ottawa and Penticton data:

svalgaard_radioflux_fig6

. Figure 7, above. In any event, the change is but small.”]svalgaard_radioflux_fig7Adding 3% to the Ottawa flux before 1991, rescaling the Japanese measurements to the thus corrected Canadian series, and computing the average flux from the two series gives us the composite series shown in Figure 8 below. All of these adjustments are very small, though, and do not substantially alter any conclusions drawn from the measurements. Although the microwave flux measurements are said to be absolute, a further correction [multiplication by the ‘URSI’-factor of 0.9] is required to get the ‘real flux’. We shall ignore that constant factor as only the relative variation is of interest here.

svalgaard_radioflux_fig8

The red and green curves in the composite graph show the Canadian and [scaled] Japanese series going into the composite. On the whole, there is substantial agreement and the microwave flux seems well-determined.

One can now ask how this measure of solar activity compares to other measures, in particular the sunspot number [the Wolf Number]. Anticipating a finding described later, we correlate the sunspot number against the F10.7 flux (Figure 9) for the interval 1951-1988, and obtain a purely formal polynomial fit [as the relationship is not quite linear]:

svalgaard_radioflux_fig9

The fit is good (R2 = 0.977) up until ~1989.0 after which time the observed sunspot number falls progressively below the fitted number (Figure 10):

svalgaard_radioflux_fig10

To quantify the drift we divide the observed sunspot number by the fitted one. When the sunspot number is very low [near minimum, marked by m; worst case, zero] that quotient becomes very noisy or meaningless, so we plot only cases where the sunspot number was above 5 (Figure 11):

svalgaard_radioflux_fig11

The progressive drift is much larger than the 3% correction and is therefore not due to the correction. It seems inescapable that the relation between the sunspot number and the microwave flux has changed significantly in recent years. Another way of showing this is Figure 12:

svalgaard_radioflux_fig12

Ken Tapping has come to a similar conclusion (from the 2009 Space Weather Workshop: http://www.fin.ucar.edu/UCARVSP/spaceweather/abstract_view.php?recid=995):

“The Changing Relationship between Sunspot Number and F10.7”:  Sunspot Number and the 10.7cm solar radio flux are the most widely-used indices of solar activity. Despite their differing nature and origins at different places in the Sun, these two indices are highly-correlated to the point where one can be used as a proxy for the other. However, during Solar Activity Cycle 23 we started to see a small but definite change in this relationship…”

So far we have been on the [relatively] firm ground of data analysis, but when it comes to an explanation of the changed relationship, we enter the realm of pure speculation [for now]. Three obvious hypotheses present themselves:

1)      The sunspot counting procedure or observers have changed with resulting artificial changes of the sunspot number as they have in the past.

2)      Changes in the Corona or Chromosphere accounting for additional F10.7 emission.

3)      Livingston & Penn’s observations [http://www.iop.org/EJ/article/1538-4357/649/1/L45/20946.web.pdf?request-id=e22b7626-e93b-4ce3-b6f1-a999655b8888] that the sunspots are getting warmer during the last decade, leading to a decreased contrast with the surrounding photosphere and hence lessened visibility, possibly resulting in an undercount of sunspots.

There has been some criticism of SIDC and SWPC recently related to counting small pores, changing the count inexplicably, and various mistakes, but it seems to this writer that these problems would not be serious enough to account for the continuous and progressive drift shown in Figure 11. The near constancy of the flux at minima since 1954 argues against a change of the physical conditions at the source locations, leaving the exciting possibility that Livingston & Penn may be correct.

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Fluffy Clouds (Tim L)

The watts effect is here.
The Cycle 24 plage region has finally produced a small sunspot. It has received the number 1017 by NOAA.
Thank you Lief for the post!
“Dr. Leif Svalgaard as guest author’

Bill Yarber

Two qestions come to mind:
1) What changed in the instrumentation or the method used to detect and/or count sun spots in 1989?
2) What, if anything, changed in the Sun in 1989?
Also, is there any proxy that might be used to calculate the F10.7 values during the previous minimums to see if the relationship between sun spot numbers and F10.7 values shifted prior to the onset of a minimum?
Very interesting article, who would of thought that our Sun can change?
Bill

Steve Keohane

Interesting Leif. If Livingston & Penn are correct, then something is shifting as regards the dynamics of the sun. Any hypotheticals on what hotter sunspots may imply about the solar environment, and resulting output in radiation?

David Holliday

Dr. Svalgaard,
I wanted to be one of the first to say thank you for your contributions in the comments and even greater thanks for your article. I look forward to future articles.

Terry Jackson

So if they get warmer, could they possibly become invisible to the naked eye? And does this correlate positively or negatively with previous solar minima? Or do we have enough data to know?
Thanks for the article and explanation.

Bill Yarber (21:16:53) :
1) What changed in the instrumentation or the method used to detect and/or count sun spots in 1989?
Nothing we know off. And I don’t think anything changed [for other reasons which I’ll address in another article]
Also, is there any proxy that might be used to calculate the F10.7 values during the previous minimums to see if the relationship between sun spot numbers and F10.7 values shifted prior to the onset of a minimum?
Yes, there are and we can go back to the 18th century on this, but that is anther article.
Steve Keohane (21:19:27) :
Any hypotheticals on what hotter sunspots may imply about the solar environment, and resulting output in radiation?
Would just be speculation at this point. One can think of many things…

steptoe fan

As the two sites for measuring are not on the same circle of latitude ( i believe ) can you dismiss this as a reason why the data would not closely correlate ?
can you briefly describe the hardware, especially the antenna, used to recieve the emmissions.
here on earth, we tend to think of RF as being either horizontally, vertically or circular polarized. I do believe as you describe the emission sources, what we are receiving is “randomly polarized”. could antenna hardware be further refined so as to better categorize the source emission means ?
perhaps hotter sunspots suggest that they are originating at a different layer of the suns interior which might lead one to wonder if the sun is going through a more dramatic state shift ? very interesting article – thanks !

steptoe fan (21:33:06) :
As the two sites for measuring are not on the same circle of latitude ( i believe ) can you dismiss this as a reason why the data would not closely correlate ?
except they do correlate very well…
can you briefly describe the hardware, especially the antenna, used to recieve the emmissions.
The link provided http://www.hia-iha.nrc-cnrc.gc.ca/drao/solar_e.html has more details, otherwise the Tanaka article referred to.

p.g.sharrow "PG"

Leif Svalgaard: thank for your clear and informative article on solar microwave output. especially the graphs. As a visial minded animal, pictures are more informative to me then words. Now I have a better grasp of your point of view on solar output vs climate.
AS to the sunspot descripency over the last two cycles, it would appear that the criteria of observation and count may have changed, most likely in 1978. I many times, have found a slight change in data is due to an “improvement” in data collection technique.

ujagoff

THAT was a good read..
Thanks for that.
But does the last sentence mean to say “exciting”?

Thank you for a very informative posting. A couple of items to consider…
1) Could the discrepancy actually be worse than the numbers show? With the advent of SOHO we’re seeing, and recording as spots, fleeting “sunspecks” that would have been difficult to see many years ago. If anything, this would push the curve up, and bias towards a positive anomaly, rather than the negative one we see now.
2) Is the drop consistent enough that you can extrapolate it? If so, does it indicate zero sunspots by around 2014 or 2015?

geo

Hmm, my previous didn’t show up as awaiting moderation, so now I’m not sure if it went thru. At any rate, if it did you can delete this one. . . but you have a misspelling of exciting in your final sentence.

REPLY:
Thanks, fixed. The word “Nazi” as in “spelling Nazi” triggered the spam filter. – Anthony

Bravo. It raises the profile of all blogs to have phenomena explained by a true expert at a level that is near explicable. Three cheers for the interactive forum and four for the teacher.
A request: Can we have an article exploring the variation in the power of radiation that is shorter in wave length than the visible?
What can we expect in terms of variation in short wave radiation as the spots disappear? Will this affect the stratosphere?

fred

Dr. Svaalgard (or anyone who knows):
Do we track conditions in the heliosphere on any consistent and broad (non-local) manner?
Have these conditions shown any relationship to the Solar cycle?
Have they shown any patterned or consistent fluctuations in the last few decades (or however long the data covers)?

erlhapp (22:17:48) :
What can we expect in terms of variation in short wave radiation as the spots disappear? Will this affect the stratosphere?
The spots are not important, the magnetic field is. and it will still be there, so I don’t expect any pronounced effects on solar radiation. One might even speculate [wildly] that since there now are no dark areas anymore, that radiation might go up… [and that perhaps TSI during the Maunder Minimum was higher than today 🙂 ]
The stratosphere will be affected if UV is, but the troposphere very likely not in any great measure [making a differnce]. But all of this are just wild guesses, we’ll have to wait and see and MEASURE as much as we can [in spite of governments trying to cut funding for science that is already settled 🙁 ]

fred (22:34:27) :
Do we track conditions in the heliosphere on any consistent and broad (non-local) manner?
Yes we do. Cosmic rays are measured and can be inferred in the past for thousands of years. Geomagnetic activity tells us about the strength of the solar wind as well, and has been measured for more than 250 years.
Have these conditions shown any relationship to the Solar cycle?
Yes they have: they vary with the solar cycle.
Have they shown any patterned or consistent fluctuations in the last few decades (or however long the data covers)?
They have shown that the solar wind right now is very much what it was a century ago.

p.g.sharrow “PG” (21:56:36) :
AS to the sunspot descripency over the last two cycles, it would appear that the criteria of observation and count may have changed, most likely in 1978. I many times, have found a slight change in data is due to an “improvement” in data collection technique.
For several reasons, I don’t think so. For one, it seems that there is an ‘undercount’ now. We are seeing TOO FEW sunspots. This does not look like an ‘improvement’ in data collection…
Walter Dnes (22:09:47) :
1) Could the discrepancy actually be worse than the numbers show? With the advent of SOHO we’re seeing, and recording as spots, fleeting “sunspecks” that would have been difficult to see many years ago. If anything, this would push the curve up, and bias towards a positive anomaly, rather than the negative one we see now.
But since we seeing a negative one now, that argues against a bias, unless the situation is even worse [as you say]. If we didn’t count the specks we would see even fewer spts. This is all very exciting and we’ll just have to see. Bill Linvingston in an email to me today “Sunspots today are behaving like a Cheshire Cat: the smile is there (magnetic fields) but the body is missing (no dark markings).” I had actually thought about using that in the title of the article, but I didn’t want to steal his ‘thunder’.
2) Is the drop consistent enough that you can extrapolate it? If so, does it indicate zero sunspots by around 2014 or 2015?
Extrapolate yurself. It is anybody’s guess.

@Leif… A solar sneeze is climate pneumonia on Earth. From your article, it seems that warmer years are for coming. Hotter sunspots, (probable) higher loads of energy the Sun will release. It’s important to know how much energy can be stored by oceans. Thanks for sharing your knowledge, Leif.

deadwood

Thanks Dr. Svalgaard. Just enough dumbing down for this geologist to (mostly) follow.
One question: Do you think the change in slope of tail of cycle 23 have any connection to the apparent changes in the nature of sunspots? And if so, what would be your explanation.

Ray

Hi Leif – that is a great article and I better understand where you come from now for your predictions. So, you expect the next cycle to look somewhat like cycle 20, or worst?
Do we observe the same cycles in other stars?

savethesharks

Extremely informative. Great science (would not expect any less from the author). Many thanks.
Chris
Norfolk, VA

Claude Harvey

So, the leopard hasn’t changed his spots. They’ve just bleached out so we can’t see them anymore. Jeez!

Read with fascination if not full understanding, Leif. Thank you.
Would you, or your 11 years old grandson, tell me (relative to these words above “…that the sunspots are getting warmer…”) the temperature of a sunspot and the temperature of the surrounding solar surface?

steptoe fan

yes, they do correlate very nicely, until recently … excuse my attempt at a question that answered itself, upon reflection ( wasn’t the best wording either ).
thanks again .

Pat

“Leif Svalgaard (22:53:27) :
But since we seeing a negative one now, that argues against a bias, unless the situation is even worse [as you say]. If we didn’t count the specks we would see even fewer spts. This is all very exciting and we’ll just have to see. Bill Linvingston in an email to me today “Sunspots today are behaving like a Cheshire Cat: the smile is there (magnetic fields) but the body is missing (no dark markings).” I had actually thought about using that in the title of the article, but I didn’t want to steal his ‘thunder’.”
Cracking analogy. I don’t want to appear a numpty, but if the “spots” are there (magenetic fields) but missing the body (no dark spots) could not only imply, as suggested earlier, that the “spots” are hotter thus harder to “see” but surely also the Sun could be “cooler”, closely matching the temperature of the spot, too?

Rik Gheysens

Your hypothese nr 3:
“Livingston & Penn’s observations that the sunspots are getting warmer during the last decade, leading to a decreased contrast with the surrounding photosphere and hence lessened visibility, possibly resulting in an undercount of sunspots.”
I found this article
http://www.lowell.edu/users/jch/sss/blog/?p=133
suggesting a “cycle-related oscillation in umbral field strength and intensity” and arguing against the proposed steady trend. So there seems be no basis for the vanishing of the sunspots in 2015 as worded by Livingston & Penn! Certainly there is a vanishing, but not linearly.

Disputin

I’ll join many others here in thanking Dr, Svalgaard for such a lucid explanation.
Now for a question that is probably outside his field: It seems that the geomagnetic field has been losing strength for some time and there has been speculation that it is about to flip polarity again. Any possible connection?

Well if Radio flux is proportional to Sunspots, then one would expect the baseline of all the Radio flux minima to be identical, would you not?
After all, you cannot have a negative number of Sunspots.
.

Alex

From 12 to 18 goes the sunspot number,,,
yet GONG images from 15 May: BB, UD and ML show blank. Not even a blurry plage today.

bill

Leif thank you for your always informative posts, and thank you for tirelessly answering the same questions in good spirit!!
On the difference in levels between sites. Presumably the beam width (and pointing accuracy) of the dish is exactly the same? If one of the dishes has a narrower beam that misses some of the suns disk perhaps this could explain the very small difference (or are they not focused and take a general sky background?)

>>From 12 to 18 goes the sunspot number … yet GONG images from
>>15 May: BB, UD and ML show blank. Not even a blurry plage today.
What are they counting – pinpricks? Or do I need stronger reading glasses?
http://sohowww.nascom.nasa.gov/data/realtime/mdi_igr/1024/latest.html

Les Francis

ralph ellis (02:02:48) :
What are they counting – pinpricks? Or do I need stronger reading glasses?
Maybe some of those dead pixels?
Whatever spots are in view will surely fade to background within 24 hrs

Walt Stone

Thanks, Leif. You’ve shifted my focus.
Is it then complete speculation to suggest that during historical solar minima, some sunspots were not counted because the spots warmed up to the extent they couldn’t be seen?
From the Livingston & Penn paper linked in the article, this is from the last paragraph:
If 1500 G represents a true minimum
for spot magnetic fields and the field strengths continue
to decrease at the rate of 52 G yr-1, then the number of sunspots
in the next solar cycle (cycle 24) would be reduced by roughly
half, and there would be very few sunspots visible on the disk
during cycle 25.

Overall, it’s kind of reassuring to know there’s still some magnetic activity going on (10.7cm) even if there’s a lower amount of sunspot activity to show for it.

Allen63

Leif,
Very clear exposition — and educational for me. Please write again.
I guess ‘time will tell’ if the ratio of spots to flux is something that also cycles on some time scale.
I apologize, but I still see a ‘gross’ visual correlation between cycle ‘energy under the curve’ and lagging earth temperature (which backs up a more detailed math model I did that says the same — without proposing a mechanism). Because of your comments over the previous months, I tentatively believe the sun’s absolute measured output does not vary sufficiently to explain that. In that connection, its great to have a credible Solar Scientist posting here (and at CA) — who is willing to educate ‘the masses’ of climate aficionados (like myself).
Anyhow, your exceptionally clearly written PDF has become a welcome addition to my permanent electronic library.

paul

Are sunspots tracked at a wavelength outside of visible light at all? IR, UV etc. If you compared those counts with visible light counts you could tell if there were “invisible” spots.

peter vd berg

i’m still trying to get my head around the relevance of this information, vis a vis the infinitesimally small period of observation against the projected lifespan of the sun.
It’s to me like watching a movie frame by frame. Whilst one frame might be still part of a current scene, the next frame can be part of the next scene of the movie. Taken like this the entire film content gets completely obfuscated.

Lindsay H

leif
The spots are not important, the magnetic field is. and it will still be there, so I don’t expect any pronounced effects on solar radiation. One might even speculate [wildly] that since there now are no dark areas anymore, that radiation might go up… [and that perhaps TSI during the Maunder Minimum was higher than today
Very nice article:
how much do we understand of the processes that create the variations in the magnetic field, and why the minimum flux seems to be a constant. could some error or factor in the distance adjustment of 7% contribute to the variance we are seeing? I note that CME’s during mimimums seem to be much more powerfull than during periods of intense solar activity, what process could explain that ??

rbateman

I’ll do a little extrapolation on my own: The contrast limits (the L&P) seems to have dramatically nose-dived after mid January 2009. To the point where even SOHO is being strained.
A year ago, contrasts of 4to1 and better on SOHO were the good stuff.
Today, 1.5to1 is a fleeting high point on days where 1.05to1 is the norm.
We could be having a series of spots occuring at the low range of L&P curve, or it may have tailed over/accelerated.
Enjoy any sunspots you may see.
No telling when they will return, as that is not a subject that L&P sheds any light on.

Alan Chappell

Is it not the time to put a satellite on the other side of the sun ? Wishful thinking

rbateman

ralph ellis (02:02:48) :
You need an image processing program. Take the GONG images and apply an exponential stretch, or something similar. Your jpeg scale is 0 to 255. You need to highlight differences of 10 or less in greyscale.
Pixels of 237 are not normally distinguishable from adjacent pixels of 244, 255 being totally white, 0 being black.
And even at that, 1.029 to 1 is a poor contrast even when stretched.

Katherine

Thank you for that very illuminating article, Dr. Svalgaard. I believe I have a better understanding now of your stance of TSI nonvariability. I am left with one question: if the 10.7 cm radio flux graph produced by SWPC in that announcement on their web page was “just wrong,” what is the correct one supposed to look like?

Tim Groves

Dr, Svalgaard, thanks so much for such a clear explanation that has taught me more about the solar radio microwave flux than I had ever imagined there was to know.
Let me take the liberty of asking a few questions.
On the appearance of sunspots, my understanding is that they occur when magnetic flux tubes in the convective zone extend through the sun’s visible surface. So if we are seeing very few sunspots at present, this means that very few magnetic flux tubes are emerging through the surface. But does this mean that there is any less magnetic flux activity or merely that the regions of magnetic flux remain below the visible surface?
Since sunspots are cooler than the rest of the surface, does their absence make a measurable difference to the observable temperature of the surface, or would this difference be so small that it would be swamped by other variations?
Can differential rotation of the sun at different lattitudes account adequately for the waxing and waning of sunspots over the circa 11-year solar cycle?
And lastly, what other more speculative hypotheses (besides the three “obvious” ones you listed) have been put forward to account for the change in the relation between the sunspot number and the microwave flux over the past 20 years? I know the late Dr. Theodor Landscheidt’s theories are frowned upon in polite circles, but is there any chance that planetary motion is involved? Or could the sun be “breathing” as in going through a cycle that repeats over a timescale on the order of centuries due to its internal dynamics.
I hope you’ll forgive me firing off a bunch of questions that may have obvious answers to anyone who has studied solar physics, and please don’t feel under an obligation to provide lengthy answers. But I think this post is a golden opportunity to clarify some basic points on a fascinating subject that is a bit of a mystery to the laymen among us.

Sean Houlihane

Very nice article. The next year should be interesting – we should see how the relation evolves as the flux returns to the level where the ratio can be calculated again, and also if that flux increases slowly or quickly.

Louis Hissink

Leif,
It would be interesting to review your data in terms of the plasma model, as formulated by Hannes Alfven and his successors.
I personally am not technically competent to do so, but maybe Anthony Peratt, or Wallace Thornhill could be approached?

TonyS

Now even the sunspots are getting warmer… SCNR
Interesting post! Well we live in interesting times, let’s see what we learn from the next sun cycle!

Rick K

Many thanks to Dr. Svalgaard for this informative article. I would like to add my request to others posted here that Dr. Svalgaard post more of these well-written and informative articles dealing with solar phenomena.
As we all watch (with different levels of technical solar understanding) this upcoming solar cycle unfold, Dr. Svalgaard’s deep but understandable articles would be most welcome.
Obviously, on this site there are many who want to learn and would benefit from Dr. Svalgaard’s expertise.

kim

Leif, does your prediction for the sunspots in the coming cycle account for the invisibility of some of them? In other words, will you have to change your estimate because some of what you expected will only be plage areas?
============================================

TonyS

Alan Chappell (03:49:27) :
Is it not the time to put a satellite on the other side of the sun ? Wishful thinking

I had that thought yesterday as well, and tempting as it is, but I guess the problem is not that we don’t see the other side (the sunspot number averages out over time anyway, I guess)
And to get a fuller image of the sun a second pair of STEREOs (trailing or leading the current one) would suffice (and have not the nasty problem how to communicate with a space vehicle stationed at the sun-earth L3 Lagrange point…). And maybe we could have the second pair of STEREOs have better equipment than and not the problems of the current pair. Ah, now I am daydreaming…

Jim Hughes

erlhapp (22:17:48) :
What can we expect in terms of variation in short wave radiation as the spots disappear? Will this affect the stratosphere?
What part of the stratosphere are you talking about, tropics, polar, and at what height ?

Leif – also add my appreciation of your lucid work.
If I have understood your conclusions:
1. There is variation in solar output over the 11 year cycle with TSI being 0.1%, and UV varies by more – at 8%? and also the aa index and radio signal drop down in the cycle troughs – we can also see a variation of a few percent in the modulation of galactic cosmic rays. These are the factors we can be sure about.
2. There is a growing consensus that over centennial time scales the TSI has not varied in the sense that it could have been lower in an absolute sense, and likewise the magnetic flux and the UV flux – this coming after a decade or more of studies that seemed to show a past period of lower TSI by 0.3% (Lean and others); though there is less consensus that the magnetic field has not been lower because there is radio-isotope data that appears to show higher levels of cosmic ray penetration (the counter argument being that the isotopes of beryllium, for example, could show fluctuation due to other environmental factors).
3. However, let us assume that Leif is right – and that none of the solar factors of interest to climate studies has been lower in the past than the current low which we presume to be a trough between 11 year cycles – but which might also herald a longer ‘quiet sun’ period – the question then arises, ‘What about the dozens of peer-reviewed paleo-ecological studies that find correlations with past climate proxies (e.g. stalagmites and sediment studies) with the solar cycles – with varying periods of 11, 22, 80, 220 and 400 years, with a 1500 year cycle possibly linked to ocean circulation).?’
4. We would then be left with the only option for causation being the LENGTH of the solar quiet period. In normal circumstances it is only 2-3 years in the trough of the cycle (and it is this signal that Svensmark picks up in cloud fluctuations; others pick up in UV and upper atmospheric effects, and Camp and Tung pick up in a 0.2C sea surface temperature response) – so we have to assume that SOME FACTOR in that 11 year variation is having this effect – however it may be amplified (the TSI alone is not thought powerful enough, so cloud cover changes are the main suspect, but UV is also there with a possible effect on the polar vortex);
5. Thus, when we consider the Maunder Minimum, we should be thinking of the CUMULATIVE effect of all those years at the minimum – whether it be 3% more cloud, 0.1% less TSI and 8% less UV………….and given that the MM was only 0.5C lower globally, it is not that hard to imagine these changes being enough – espcially if there are shifts in the jetstream, polar vortex, Arctic oscillation and the storm tracks across the Pacific and Atlantic.