Are solar flecks being counted?

Posted: April 9, 2012 by tchannon in Solar physics

Figure 1

A frequent question in recent years is whether solar sunspot activity is being exaggerated by including very small marks in the count. This question implies inconsistency in methodology over time.

Recent other work on solar data puts me in a good position to quickly approach an answer, all the resources are already on disk here.

The quick answer is: Not obviously.

I invite further investigation, data used here is provided.

A reasonable way to address this problem is compare total sunspot area with sunspot count on the basis that counting many nothings adds no area. Detail dispute on this, please check the raw data, I haven’t.

Dr David Hathaway now maintains the NASA/Greenwich solar dataset after the British decided to not bother funding something important but seen by them as unimportant (yes politics, I do not like these people, are not technical people nor scientists). The project is a labour of love without proper funding. It is the source used to create the Butterfly diagrams.

“The Royal Greenwich Observatory data has been appended with data obtained by the US Air Force Solar Optical Observing Network since 1977. This newer data has been reformatted to conform to the older Greenwich data…”

Web page “The Sunspot Cycle” on NASA servers.

The dataset which runs from 1874 is not useful as a time series without major post processing for which I wrote code some time ago. In this case a data extract of sunspot area for north and south processed to daily. (in spreadsheet, didn’t update the data to current, month or so missing at the end)

Daily data over 100+ years cannot be directly plotted so I decimated to a more reasonable monthly via signal processing (trivial to do here, not set up to do pocket calculator method). Low pass filter at 60 days and pick off monthly at the right time offset. The filter will ring slightly on this data, unimportant. End correction is used. (ask if you need to know)

And then we look


Figure 2

I hope those line up. Total is simple sum north+south

Putting the SSN plot next to the total area plot make a compare easier.



Figure 3

Normalising this kind of data is unlikely to work perfectly but is passable. I used RMS and std dev. on both datasets as a cross check because the intent was moving the area data to SSN scaling. The processed SSN dataset matches the original, cross check successful.

Figure 3 does show some defects, zero offset for example but is minor. In broad terms the match is good. A better method would be to decimate daily SSN data so that both data were commonly filtered but I decided against this to avoid arguments over validity. Illustratively Figure 4 following shows the minor difference if that was done, not used here.


Figure 4

Plot overlay using different trace widths. There are subtle detail differences primarily from artefacts in the standard method, leakage because of lack of spatial control. Signal processing has other insuperable minor problems.

Dataset difference

Figure 1 repeated below, is the simple subtract of the two normalised data. No plainly obvious difference. This shows that area and count are essentially identical and could proxy each other.


Figure 1

A more detail examination I leave to any interested readers.

An XLS is here, portable 97/xp/2000 format, 9M, plots are left in but won’t survive into other packages, delete and recreate as you wish.

Post by Tim Channon, co-moderator

  1. tallbloke says:

    Excelllent work Tim!

    This needs a bit of thinking about before serious comment, but my first thought is that this leaves Leif with a problem with the 20% reduction of the Waldmeier count he uses to ‘get rid of the C20th ‘grand maximum” doesn’t it?

  2. tallbloke says:

    Another quick thought is that since a lot of the complaints about flecks being counted was concerning their use to nix spotless day runs becoming record breaking, the total effect may well be smaller than thought. Where does this leave Geoff Sharp’s layman’s count in your view?

  3. tchannon says:

    I mostly do information. Presumably what Leif is dealing with is consistent with all the data but there is another twist. He tends to rely on radio data, which is nothing like as good as the fixed up datasets make it appear. Long story in this where a lifetime in signals etc. makes me wary given known changes in equipment and practice only apparent on detail knowledge, which I have.

    The twist is radio data commences 1946 whereas the area data goes back many more years. What is being compared is a fixed up dataset with ssn but was the fixing up independent of ssn?

    Whatever the case please be careful, egg can fly very easily. My inclination is ignore Leif. We might need Hathaway on side.

    Geoff Sharp? Sorry I don’t know about that. The web site he uses is inaccessible, visually too much for me. Found it, had a quick look fully sanitised, forget it. Someone will have to tell me.

  4. Roger Andrews says:


    Do you know how sunspot area was calculated?

  5. tallbloke says:

    how sunspot area was calculated?

    “Right Fred, take this end of the tape and go round the other side. Watch them hot bits, and for gawds sake don’t fall in.”

    Hathaway usually answers polite emails.

  6. Roger Andrews says:

    I assumed the guys with the asbestos tape measure knew what they were doing, so I took Tim’s sunspot area numbers and divided them by the number of sunspots to get the area of the average sunspot at any time

    Here’s what I got:


  7. tchannon says:

    Not clearly.
    There is area and there is corrected area, presumably for field of view. Beware mistakes on my part, this is unchecked work, although a good match suggests there isn’t a problem.

  8. tchannon says:

    Wot you got. Hmm… Looks like near zero divide.

    Lets do this on daily data. (all data already in spreadsheet)

    Update: Bad idea, I forgot the zeros! Need to think how to handle this.

    Try this, divide zero put as no data, interpolate, changed filter to 0.5 year to better handle periods of zero. Odd looking data but what does it mean?

  9. Roger Andrews says:

    “Area” is in column U on your spreadsheet but I don’t see “corrected area” anywhere.

  10. tchannon says:

    Column D is the raw area data. SIDC sheet has daily SSN. Best work before processing for plot.

  11. Sparks says:

    The Catalog of Naked-Eye Sunspot Observations and Large Sunspots from 165 BC to AD 1684 Compiled by Axel D. Wittmann is very interesting, (ANCIENT_DATA), I think it’s a good indicator (by proxy) of the sun having activity during a typical solar cycle.
    Has anyone hindcast this data from the length of a typical cycle and had a look?

    Just purely for interest I couldn’t see data like this being used other than to imply that the sun had sun spot activity and a certain date in the past, Naked-Eye Sunspot Observations wouldn’t be flecks, Some accounts sound like major activity.

    [co-mod, interesting, but I hope you can see properly, still seeing artefacts from those pages.


    “Catalog of Naked-Eye Sunspot Observations and Large Sunspots
    165 BC to AD 1918

    By Axel D. Wittmann, Goettingen, Germany

    Large (‘naked-eye’) sunspots may serve as one of the primary indicators of
    solar activity; their distribution shows the typical features of solar
    activity (11-year cycle, butterfly diagram, bimodal maxima, Maunder-type
    maxima and minima, etc.). Historical naked-eye sunspot observations are
    one of the very few direct (non-proxy) means of studying solar activity
    during the past.

    This cataloge contains observations of large sunpots (or what may possibly
    have been a large sunspot!) with the naked eye. ‘Modern’ spots (more
    recent spots observed telescopically) are only included if they were large
    enough to be (in principle, at least) visible to the naked eye.

    When trying to interpret the data, and in particular the ancient Chinese
    observations, note that they are not at all systematic, i.e. ‘dense’ in
    time (or statistically ‘complete’), but were made more or less by chance,
    or were often cited inaccurately in the chronicles! In particular, the
    ancient astronomers were trying to determine the phase of the new moon
    (for calendar purposes), and that is why often sunspots were preferrably
    detected near the day of new moon (whereas their actual ‘maximum’ was
    sometime else): So be careful and don’t mis-interpret the meagre

    Data from 165 BC to AD 1684 were compiled by Axel D. Wittmann, University
    Observatory, Goettingen, Germany, and Zhen-Tao Xu, Purple Mountain
    Observatory, Nanjing, China; cf. Ref. [1].

    This data has been updated and expanded (in particular for the time from
    1685 to 1918) by data taken from the catalog of Kevin K.C. Yau and F.
    Richard Stephenson, University of Durham (cf. Ref. [2]) by A.D. Wittmann
    in 1988.

    The ‘modern’ observations (after AD 1764, and in particular those of the
    20th century) were compiled by A.D. Wittmann; if possible they include the
    measured area and the observed heliographic latitude. The date usually is
    that of the CMD passage.

    Electronic copies of the catalogue are available from the author upon
    request. A downloadable version is available from the WDC-A for Solar-
    Terrestrial Physics at Boulder (for more information please contact
    Dr. Helen Coeffey, Editor Solar-Geophysical Data,


    [1] Wittmann,A.D., Xu,Z.T.: 1987, Astron. Astrophys. Suppl. 70, pp. 83-94.
    [2] Yau,K.K.C., Stephenson,F.R.: 1988, Quart. J. Roy. Astron. Soc. 29, 175.

    Author’s address:

    Dr. A.D. Wittmann, University Observatory, Geismarlandstr. 11,
    D-37083 Goettingen, Germany”



  12. Roger Andrews says:


    I think there’s something squirrelly about the data here. I’ll take another look in the morning if I get time.

  13. tchannon says:

    Good, keeps things honest.

  14. Sparks says:


    Thanks, That’s the strangest thing! I was under the impression that this compiled data was
    considered a proxy of sorts?
    It’s interesting because I thought this data was considered a proxy and It put me off doing any real study into the Ancient naked-eye accounts of solar activity.

    If it’s not a proxy it has opened up a whole new area of interest for me.

  15. lsvalgaard says:

    No, it does not conflict with the Waldmeier Jump. check slide 34 of

    [Reply] Sorry Leif, all comments from WUWT team members are on hold pending an explanation for my being banned from commenting there. I hope the issue can be resolved quickly so that normal service can be resumed. Thanks for your patience. By the way, why do the sunspot areas data agree with waldmeier?

  16. lsvalgaard says:

    Perhaps a simply graphic will make it clear to you:

  17. J. Seifert says:

    Dear Tchannon, I would like to compare to
    Geoff Sharps page… I believe there are valuables
    to be found….
    What is his page called?
    Thanks in advance

    [Reply] – TB