Solar polar magnetic field misunderstanding and data matters

Posted: March 31, 2015 by tchannon in Analysis, Solar physics

A resent post by Roger and comments thereon led to my  realising there are misunderstandings on the intepretation of the polar field relationships.

Wilcox Observatory[1] measure and publish a time series of the solar polar magnetic field, a difficult measurement. Started 31st May 1976, data point every 10 days.


Figure 1, straight plot of f10.7 radio noise[3] as a proxy for solar activity and mean solar polar magnetic field[1].

Firstly here are some clarification notes.

The polar field is not the interplanetary field[6] indirectly associated with terrestrial cosmic ray flux. This field at earth roughly follows the F10.7 / sunspot shape, is very noisy.

Neither is it the Livingstone & Penn[2] finding about the change in sunspot magnetic field possibly reducing with time.

Particularly the polar field[1] passes through zero field at about solar cycle maximum. It is believed the solar maximum, which is a matter of opinion published after the event occurs 6 months to 3 years after the zero crossing. The maximum polar fields occur when the solar activity from a sunspot or radio noise perspective is at a minimum. This phase difference might be counter-intuitive.

Also remember the solar magnetic field has half the frequency (twice the period) of the sunspot cycle.

In addition alternate sunspot cycles have opposite polarity magnetically but the human eye cannot see the difference, all look the same. In reality there are a mixture a lot of the time. [4][5]

Polar field relationships


Figure 2. Differentiating the low pass filtered mean polar field to extract a shape / change trace, probably a novel result. Filter uses end correction.

This is where things get interesting. The polar field as a rule of thumb transits zero field a little before the sunspot maximum which we can see at years about 1980, 1990 and 2000. We can also see the greatest magnetic field is around sunspot cycle minimum.

My opinion is the magnetic field tends to stabilise the sun hence a lower field when there sun is active, stronger field when it is passive. There are however contradictions, unsurprising in a mysterious object.

In differentiating[8] the curvature and rate of change is brought out. This shows maximum values about 1980, 1990 and 2000, about the same as zero crossing points.

The current sunspot cycle is peculiar. The polar field zero crossing is past and there appears to be a peak in the differentiated so we are probably past or at sunspot cycle maximum. I’ve not seen official confirmation, generally a late announcement. However the Talkshop yields up, I posted on this during 2012, a report from the Japanese Hinode satellite team.

This was taken as jumping the gun but neither has the effect been seen before, moreover the north and south pole do not seem to change concurrently. Put together this means that signs of a zero field forming appear earlier than previously thought. More than three years after then also points to currently past sunspot cycle maximum.

The compromise filter and differentiator

This was done to try and gain a useful result, there is no right or wrong.

Applying the differentiator to the polar field data as-is produces massive noise, the process is very sensitive to data noise.


Figure 3. Effect of filter cutoff.

Unfortunately the WSO Polar magnetic field data is compromised, a matter I’ve written on in the past. Briefly it is a difficult measurement done by telescope. The geometric view of the solar pole varies by time of earth year and in consequence there is a modulation effect on the data. A spectral analysis of the data


Figure 4. A spectral analysis (windowed chirp z-transform) reveals a tell-tale of amplitude modulation of some kind, a doublet. This explains the wobble visible on north and south individual data. To a degree summation cancels the wobble but this is incomplete and cannot undo related higher order effects.

The modulation is primarily between the large signal excursion and the varying field of view which changes with an annual period. (technically a product of terms (literal multiplication)). The usual sum and difference computations confirm this, details not part of this work.
Work on this a few years ago as a remedy only achieved a partially successful synchronous demodulation. The data collection has varied over time so this probably in my opinion irrecoverable. I hope someone succeeds.

An example of similar modulation in a natural system can be seen in Spectrum of 100-kyr glacial cycle: Orbital inclination, not eccentricity[9]

A closer look at the published polar data


Figure 5. Probability plot of normalised 300 day low pass filtered mean data.

Looking at the data produced this extraordinary data shape where a straight line or simple curvature would be reasonable confirms the data is unsafe for detail work. Filtering noise reduction has clarified what is not obvious in straight data.


Figure 6. Probability plot of various data


Solar cycle 24 is past maximum. Attempting extrapolation based on the polar magnetic data is too uncertain.


Putting the data together is a little wrinkly so here is a portable spreadsheet of polar data and pre-decimated F10.7 data sampled concurrently with magnetic data. (2MB XLS ’97 format)

[UPDATE] Added a demonstration of modulation


Figure 7. How an approximation to the North pole data can be mimiced via amplitude modulation. One year sine trace is shown magnified 100X for clarity. DSB + C is double sideband + carrier, which is the slow signal. Plotted as points so that the granularity of the signal can be seen.




  1. WSO
  2. Long-term Evolution of Sunspot Magnetic Fields
  3. F10.7 NOAA FTP site
    link here
    F10.7[cm] is 2800MHz measured by pointing a very directional aerial (antenna) at the sun. This is a large interesting subject.
  4. Hathaway at NASA site, Backwards sunspot
  5. Slide 19 from presentation, “Hale’s sunspot polarity law”
    Whole presentation
  6. Interplanetary Magnetic Field
  7. Moderately technical presentation on F10.7 solar noise measurement at 2800 MHz
  8. Smooth noise-robust differentiators (N=5)
  9. Spectrum of 100-kyr glacial cycle: Orbital inclination, not eccentricity, Richard A. Muller and Gordon J. MacDonald, NAS 1997, open access at PNAS
    Perhaps particularly Figure 2 therein.


Post by Tim

  1. oldbrew says:

    Solar max and SH max were about a year ago according to this.

  2. tallbloke says:

    Lovely work Tim. Thanks for spending time on this.

    Still want to know the periods your software found in the polar data though. 🙂

  3. tchannon says:

    Yup that fits oldbrew.

    Reference 9 is of wider interest, cautionary when it comes to long proxy. Preprocessing data is one of the tough problems where knowing it has to be done is an important realisation. Non-linearity is best sorted before using linear tools rather than poor tools which can only kind-of work on wonky data.

  4. ren says:

    The Mean Magnetic Field of the Sun.

  5. ren says:

    A successful model for the solar dynamo must explain several observations: 1) the 11-year period of the sunspot cycle, 2) the equator-ward drift of the active latitude as seen in the butterfly diagram, 3) Hale’s polarity law and the 22-year magnetic cycle, 4) Joy’s law for the observed tilt of sunspot groups and, 5) the reversal of the polar magnetic fields near the time of cycle maximum as seen in the magnetic butterfly diagram.

  6. oldbrew says:

    ren: here’s one attempt to explain the SC – ‘Miles Mathis: The Cause of the Solar Cycle’

  7. ren says:

    “In other words, they are seeing clear evidence here of a charge or magnetic feedback loop from the
    large planets (or all the planets, but mainly the big four). This is so obvious, I have to think they are
    suppressing the information on purpose, once again to protect their pet theories. They can’t admit the
    obvious here, because it would be (and already is) the final nail in the coffin of their gravity-only
    theory. They have to pretend not to remember that the orbital period of Jupiter is 11.862 years,
    pointing at the Solar cycle, and that the great conjunction is about 19 years, since if they start along that
    path they will very soon come to a point where they have to admit I was right all along. Eventually
    they will end up where I have already been for years: with a working unified field in the Solar System
    that is capable of explaining the mechanics (and generating the equations) beneath Bode’s Law, all the
    axial tilts, the eccentricities, the albedoes, magnetic reconnection, the Coriolis Effect, Lagrange points,
    and on and on.”

  8. ren says:

    “The Solar Current article considers a possible link between solar periodic activity and orbital
    properties of the major planets i.e. Jupiter and Saturn, which might be achieved via a feedback
    as a result of energy exchange between heliospheric current and planetary magnetospheres.
    If the above is valid for the Jupiter / Saturn than the Earth’s magnetosphere should exert
    similar effect.”

  9. vukcevic says:

    The sunspot count for March from SIDC is 38.4 well down on recent peak as you can see here .
    It appears that the SC24 has peaked about a year ago.
    This is surprisingly as anticipated about some 12 years ago.
    Dr. Leif Svalgaard, referring to my ‘heretical’ approach, once said:
    “You may turn out to be correct for the wrong reason”
    For time being I’ll put stronger accent on the ‘correct’ than a ‘reason’, case of a conformation bias no doubt.
    Well, of course there might be another peak in a year or so, but I strongly doubt that it will exceed one from the early 2014.

  10. ren says:

    s you can see the solar wind speed still quite high. Therefore GCR not increased. There is also increasing pressure over the Arctic Circle.

    Increases only in the upper layers due to the action of UV.

  11. Paul Vaughan says:

    Rial counsels of flaws in Muller & MacDonald (1997):

    Rial, J.A. (1999). Pacemaking the ice ages by frequency modulation of earth’s orbital eccentricity. Science 285, 564-568.

  12. ren says:

    As you can see the solar wind speed still quite high. Therefore GCR not increased. Do not is also increasing pressure over the Arctic Circle.
    Increases only in the upper layers due to the action of UV.

  13. vukcevic says:

    Hope SDO will be fixed soon

  14. vukcevic says:

    Enter your comment here…Click on the image above to see the fault

  15. ren says:

    Vukcevic I wish the colored eggs.

  16. Bob Weber says:

    Those are some weak looking solar polar fields at the moment.

    Miles is predicting one more year for this cycle than the SWPC. I don’t know if that’ll be right, based on observations compared with SWPC predictions. The SWPC says the minimum is by Dec 2019.

    This year, based on F10.7cm radio flux, their cycle prediction is just slightly off their “low” range for daily average radio flux during the previous two months:

    Jan- SWPC “high” range was 138.4, actual was 142
    Feb- SWPC “low” range was 129.1, actual was 129.1
    Mar- SWPC “low” range was 126.3, actual was 126.4

    From (the numbers above were from Mar 9, which are updated monthly- check every month on the 10th for new prediction updates)

    According to that, for 2015, F10.7cm will go below 120sfu/day (my SST warming/cooling line) either

    High range – 118.5 November
    Mid range – 116.8 July
    Low range – 117.4 May

    The Sun appears today to have two sunspot groups, directly opposite each other, one that just rolled off out of sight, AR2305, and one that just rolled back into view, now smaller than it was during the last rotation:

    I anticipate we will be closer to the “low” SWPC range through this year, pegging the solar cool-off to this summer. Except for the weak El Nino, or a short-term solar spike(s), I expect SSTs to start dropping this summer as accumulated ocean heat content drops.

    It’s all downhill from there until SC25 max, that’s if it reaches a SSN max of >35-40, roughly, and if not, the next max, SC26, sometime around 2040.

    The ~120 line is under evaluation and will be finalized after the revised SSNs are released in August.

    Global warming is toast. Global cooling is just getting started.

  17. Bob Weber says:

    ren, F10.7cm solar flux averaged 136 sfu/day for 9 days since March 23, peaking on the 28th at 146. From Jan 26 to Feb 10, flux averaged 151 for 16 days, peaking at 172 on Jan 29. There is no corresponding pressure increase in your GPH anomaly plot for the earlier flux increase, indicating to me that the effect was solar wind driven, and less to do with UV (F10.7cm flux is a good UV proxy).

    The solar wind speed and density, hence dynamic pressure, and hemispheric power, were relatively high lately, causing another Forbush decrease, on the tail end of the last one that started with the Mar 17th geomagnetic storm. That’s were it came from, methinks. Your thoughts?

  18. ren says:

    Bob Weber note what happens when UV is high (according to 10.7).

  19. Bob Weber says:

    vuk – your earth-jupiter synod evaluation is very interesting. Did you try an earth-saturn analysis?

    I seem to see a similar sub-cycle in HadSST3, especially in more recent data (that may be more accurate), but looks could be deceiving…

  20. ren says:

    Bob Weber

  21. ren says:

    In the lower part of the stratosphere can not see the rise in pressure. Otherwise than it was in the winter.

  22. ren says:

    It seems to me that the UV is more evenly distributed over the pole than GCR.

  23. Bob Weber says:

    ren, F10.7 averaged 148 sfu/day for Jan 1-14, peaking at 157 on Jan 8. There was also an “unexpected” G3 class geomagnetic storm on Jan 7/8, that followed several two M1 flares (from )

    There were 28 M-flares from March 2 to March 17, which did iononize the upper atmosphere, but I don’t see the effect of those in your plots.

    However, F10.7 averaged 120 sfu/day from Feb 14 through Mar 4, 19 days, during the time when zonal temps were decreasing. From Jan 16-25, 10 days, the flux averaged 125, corresponding to a lesser degree of zonal cooling for that period than the later 19 day period.

    From March 8-22, 15 days, flux averaged 119 sfu/day, during the very deepest cold penetration as indicated in your zonal temperature plot. The intensity of the cold moderated from earlier episodes most likely from the seasonal obliquity change going into NH spring.

    Interesting. Perhaps a combination of UV and particle effects (joule heating) are in play.

  24. ren says:

    Bob Weber compare plot GCR and pressure over the Arctic Circle .

    The pressure increase followed about a week after a wave of GCR. Now can not see it.

  25. Geoff Sharp’s take on the solar polar fields. I tend to agree with his take on things.

    March 3, 2015 at 8:32 pm

    What is this ‘phase catastrophe’ is it a term for the slowing down of the polar fields?, because all I can see happening is the polar field reversals are slowing down and producing less sunspots. the polar fields also speed up and produce more sunspots, the sine-wave in the graph above called ‘angular momentum curve’ is identical to the speed the of the polar field reversals, and it’s very interesting that the timing of the distance between Uranus and Neptune have the exact same rate of orbital change.. I mean the correlation is absolutely staggering!

    Geoff Sharp says:

    March 4, 2015 at 2:19 am

    Hi Sparks, glad to see someone paying attention 🙂

    The “phase catastrophe” I refer to is the breakdown of the Hale cycle where one or both poles fail to change polarity near cycle max, which probably is a result of not enough reversing flux traveling to the pole during a severally reduced dynamo.

    When you say polar reversal speed I assume you mean solar cycle length, which correlates with weaker cycles being longer. In general stronger/shorter cycles occur during times of high AM but grand minimum type cycles also occur near the top of the wave. The top of the wave is always U/N together. I calculated the wave by inverting the AM values below the centre of Carl Smiths AM graph, history shows us it is the amount of movement in any direction on the AM graph that produces the largest cycles, by inverting all values under the centre point we see the true AM strength (purple peaks)

  26. From Geoff,

    This is the first time modern science can measure a possible grand minimum…we might find that grand minima are simply one hemisphere closing down. Will there be enough sunspot activity in the south to allow the transportation of the reversing flux necessary for a polarity change?…lets see how it pans out.

    My reply

    Predicting future solar activity based on when the sun was in an active mode 1830-2005 ,versus now that the sun is in an inactive may not hold up very well.

    One example of this thus far was the extreme solar lull that took place from 2008-2010.

    I think this current solar cycle will last until Dec.2021.

  27. tchannon says:

    UPDATED article with a graphic, Figure 7, demonstrating modulation.

  28. ren says:

    Will continue to be due to the location of the polar vortex.
    Currently, strong blizzards in Germany and Poland. In Scandinavia frost.

    Polar vortex is still fairly strong due to the high speed of the solar wind.

  29. oldbrew says:

    [from The Hockey Shtick]

  30. ren says:

    Polar vortex at the height of 27 km.

    Polar vortex at the height 17 km.

  31. ren says:

    Canada despite a temporary of warming will be even long to wait for spring.

  32. ren says:

    Very much snow will fall now in the Alps.

  33. Bob Weber says:

    Something odd happened yesterday. After I posted the image of the sun with the one sunspot, later in the day I noticed on both Solarham and Spaceweather that their images still showed AR2305, and no new spot on the incoming side. So I went back to the source wher I first noticed it, SolarIMG, and there were no spots, as in their image, AR2305 was just off the edge. From this morning’s SolarIMG:

    The incoming spot disappeared yesterday! Solar flux was 124 yesterday, and today with no spots, it should be less than that. Update later.

  34. Bob Weber says:

    weird, there it is again… bonkers … I just put the same link in a seperate tab, and there was no spot there! From Spaceweather just now:

  35. Bob Weber says:

    Directly from the SDO site

  36. Bob Weber says:

    “SDO is Almost Back to Normal

    SDO is now pointing at the Sun with one high-gain antenna returning science data. The other high-gain antenna is pointing in the wrong direction and engineers are working on the best way to move it to the correct direction. Science data is flowing to the SOCs but interruptions may occur as the observatory is returned to the proper state.

    Posted by Dean Pesnell at 10:40 AM” [April 1]

    Maybe this is the reason…

  37. Bob Weber says:

    Thanks ren. You are probably going to like my website, as it encompasses so much of what we talk about and includes so many image plots it’ll make your head spin… Ready soon – I’ll let you know. The image hsa not been updated since March 13. Solarham’s image is the same today, from Mar 13, here Which makes it hard to see what’s on the farside.

    See for today’s magnetogram.

  38. ren says:


  39. Bob Weber says:

    I have no idea what happened with that other spot that is no longer visible on the incoming side from here . There’s one sunspot, the one that’s just rolling off, AR2305, as seen in this image from yesterday of the whole Sun:

  40. ren says:

    Bob Weber April Fool’s Day.

  41. Bob Weber says:

    No kidding!

  42. ren says:

    Bob, I’ve seen the “disappearing” sunspot, treat it as a joke.

  43. Ren could you give me a brief description on how to read the GDAS CPC ZONAL TEMP TIME SERIES charts you send.

    Are they showing the anomaly between 60-90 N lat at various heights in the atm. through out the course of the year?

    For example on the graph you sent at 4:08pm apr. 01 is it saying the zonal temp. anomaly is plus 16 to plus 20 c for early Jan at an altitude of around 35km for the entire area between 60-90 N latitude?


  44. Bob Weber says:

    F10.7cm was 121 today. On March 28, the USAF was calling for it to be 155 today and tomorrow – they were off today by 34 sfu – quite a bit. The USAF forecast here is now calling for a 45day F10 daily average of 134 sfu, as of today. The SWPC 27day forecast for today was 145 sfu, off by 24 sfu, still a lot.

    If the Sun doesn’t produce some new sunspots soon, I’m going to have to start thinking the SWPC SC24 predictions here for lower flux are going to be accelerated, and we’ll reach monthly average levels below 120 much sooner.

    I’d be very interested in the opinion of any PRP people or any other planetary theory advocates as to what causes sunspot activity to change in either direction on a short-term basis, and how the current planetary configuration and in the future will specifically cause the downtrend in sunspot activity, and whether any upticks through to the minimum can be predicted using those ideas.

    Looking at various magnetograms, it appears the solar surface plasma is not concentrating into active regions very readily right now. What would possibly change that? It appears there is still a ways to go until most of the plasma descending from the poles reaches the equatorial band.

  45. ren says:

    Here can see that the number of spots does not coincide with the magnetic activity of the sun.

  46. Bob Weber says:

    ren, I don’t know how I missed that article when it was posted, so thanks. GOES 108 day is also a product featured on my site, with the 7 day and 3 day summaries, and the stratosphere products 😉

    The “magnetic” – really it’s the PLASMA activity – activity starts at the solar poles at the prior cycle minimum, and moves equatorward through the subsequent cycle, concentrating along oppositely polarized sector boundaries, where the sunspots are created, and where the “slow” solar wind originates, where solar flares occur and CMEs fire off, and the areas in between the sector boundaries on the sun are the coronal holes, where the “fast” solar wind originates. Preaching to the choir there I’m sure…

    The GOES satellite, ACE, and others near the Earth measure the “magnetic” – ie PLASMA – activity near the Earth a few days after it leaves the solar surface, and thus it appears out of synch with the sunspot number much of the time. The sector boundaries that the sun creates flow past the earth, along with the faster coronal hole streams, some flare-related CMEs, and filament eruption plasmas, all at various speeds and densities. So the sunspot number is really only so useful as it only describes part of the activity.

    So it’s a hodge-podge of plasma activity that starts when the solar poles “reload” during the solar minimum, and thereafter makes it way outward from there over time, and provides all the interesting things we see in the “magnetic” fields from the PLASMA activity interactions that behave electrodynamically/magnetohydrodynamically. UV from higher X-ray flux activity during higher sunspot number periods also affects planetary ionospheres, driving weather effects too via ozone.

    The PLASMA protons and electrons, and cosmic rays, provide for us ‘electric’ (-magnetic) weather effects, such as the offset polar vortex, and other events that vary with IMF intensity and direction. The PLASMA variations on the solar ‘surface’ drive the sunspot number and changes in solar flux that do correspond with and do warm/cool the Earth at ~120 sfu, according to my analysis. Others have estimated a different set point, but the point is, there is one; the exact value TBD this year.

    The Earth, like any thermal heat sink, requires a certain amount of solar energy to maintain a fairly constant temperature, a temperature that varies upward with accumulated solar radiant flux heating in mainly the ocean, and decreases over time with insufficient solar flux energy (cooling).

    How (or ‘if’) the solar plasma cycle (‘dynamo’ action?) is affected by the planets is very interesting. If the sun merely recirculates plasma in a shallow dynamo as the standard model says, how is it that the dynamo plasma activity cycle in all the solar cycles differs so much over time?

  47. Bob Weber says:

    oops, sorry oldbrew… appreciate it!

  48. ren says:

    Bob Weber 100%.

  49. Bob Weber says:

    This topical paper came out today “The solar magnetic activity band interaction and instabilities that shape quasi-periodic variability”,

  50. Table 1 page 9 left me with some questions which I ask below.

    My question is what was the parasitic polarity value,and Large scale dipole value during the recent solar lull? Was it 30G/1G respectively?

    What is the present parasitic polariy and Large Scale Dipole value at present? Is it 10G for the dipole solar strength?

    In Table 1 page 9 of paper I do not understand how Model a compares with Models b-f .

    Model a unlike the others b-f does not have a parasitic polarity value or a Large Scale Dipole value which makes it hard (for me) to reconcile the difference in the solar photosphere’s magnetic strength /configuration in model a of Table 1 versus the other scenarios presented in table 1 as shown through models b-f.

    Anyone have answers? Thanks.

  51. Along the lines of the paper I sent in my post at 5:54 Apr. 10, I would like to get some thoughts on how severe this Solar Grand Minimum which the paper suggest we are entering now might be.

    For example ,how will it compare in degree of magnitude and duration of time to the Dalton Solar Minimum and the Maunder Solar Minimum ?

    What is the latest data in the solar polar fields indicating about the magnitude of this possible Grand Minimum ?

  52. is there any probability to deviation between the angle of magnetic equator and geometric equator as from my point of view it has changed by 0.37 degree contrast i think this may be the fact return back of Russian satellite on earth also is there any relation by earth quake in “NEPAL” on 25th april 2015, also i want to ask about the fact of reverse of moon on 26th april 2015 also confirm that is there any chance of earth quake of strength of 10 equator in north “INDIA” centre near by “New Delhi” (national capital of INDIA)up to 10 may 2015.
    i m not asking for any rumour or to create any panic.

    “Submitted on 2015/05/01 at 5:24 pm

    probability to deviation in angle between magnetic equator and geometric equator.
    it is correction in earlier comment post by me”

    [moderator: Crustal stress released by the Nepal earthquake changes existing knowledge about crustal stress in the Indian subcontinent. Your text suggests a change in earth parameters but confirmation will take a long time. ]