Solar Science

A blog of solar physics

Hathaway updates: SC24 to start late, rapid increase to maximum

with 10 comments

I’ve noticed that David Hathaway is not backing down from his previous predictions that SC24 will be a) larger than SC23 and b) the length of SC24 will be approximately the same as previous cycles.

Here is the update:

Predicting the behavior of a sunspot cycle is fairly reliable once the cycle is well underway (about 3 years after the minimum in sunspot number occurs [see Hathaway, Wilson, and Reichmann Solar Physics; 151, 177 (1994)]). Prior to that time the predictions are less reliable but nonetheless equally as important. Planning for satellite orbits and space missions often require knowledge of solar activity levels years in advance.

A number of techniques are used to predict the amplitude of a cycle during the time near and before sunspot minimum. Relationships have been found between the size of the next cycle maximum and the length of the previous cycle, the level of activity at sunspot minimum, and the size of the previous cycle.

Among the most reliable techniques are those that use the measurements of changes in the Earth’s magnetic field at, and before, sunspot minimum. These changes in the Earth’s magnetic field are known to be caused by solar storms but the precise connections between them and future solar activity levels is still uncertain.

Of these “geomagnetic precursor” techniques three stand out. The earliest is from Ohl and Ohl [Solar-Terrestrial Predictions Proceedings, Vol. II. 258 (1979)] They found that the value of the geomagnetic a index at its minimum was related to the sunspot number during the ensuing maximum. The primary disadvantage of this technique is that the minimum in the geomagnetic aa index often occurs slightly after sunspot minimum so the prediction isn’t available until the sunspot cycle has started.

An alternative method is due to Joan Feynman. She separates the geomagnetic aa index into two components: one in phase with and proportional to the sunspot number, the other component is then the remaining signal. She found that this remaining signal faithfully represents the sunspot numbers several years in advance. The maximum in this signal occurs at sunspot minimum and is proportional to the sunspot number during the following maximum. This method does allow for a prediction of the next sunspot maximum at the time of sunspot minimum.

A third method is due to Richard Thompson [Solar Physics 148, 383 (1993)]. He found a relationship between the number of days during a sunspot cycle in which the geomagnetic field was “disturbed” and the amplitude of the next sunspot maximum. His method has the advantage of giving a prediction for the size of the next sunspot maximum well before sunspot minimum.

We have employed these methods along with several others to determine the size of the next sunspot cycle using a technique that weights the different predictions by their reliability. [See Hathaway, Wilson, and Reichmann J. Geophys. Res. 104, 22,375 (1999)] This analysis indicated (by mid-1996) a maximum sunspot number of about 154 ± 21. We then use the shape of the sunspot cycle as described by Hathaway, Wilson, and Reichmann [Solar Physics 151, 177 (1994)] and determine a starting time for the cycle by fitting the data to produce a prediction of the monthly sunspot numbers through the next cycle. We find a starting time of July 1996 with minimum occuring in October 1996. The predicted numbers are available in a text file, as a GIF image, and as a Postscript file. As the cycle progresses, the prediction process switches over to giving more weight to the fitting of the monthly values to the cycle shape function. At this phase of cycle 23 we now give full weight to the curve-fitting technique of Hathaway, Wilson, and Reichmann Solar Physics 151, 177 (1994). The two parameters for this fit (cycle amplitude and cycle starting time) have remained unchanged since early 1999.

Note: These predictions are for “smoothed” International Sunspot Numbers. The smoothing is usually over time periods of about a year or more so both the daily and the monthly values for the International Sunspot Number should fluctuate about our predicted numbers. Also note that the “Boulder” numbers reported daily at are typically about 35% higher than the International sunspot number.

Another indicator of the level of solar activity is the flux of radio emission from the Sun at a wavelength of 10.7 cm (2.8 GHz frequency). This flux has been measured daily since 1947. It is an important indicator of solar activity because it tends to follow the changes in the solar ultraviolet that influence the Earth’s upper atmosphere and ionosphere. Many models of the upper atmosphere use the 10.7 cm flux (F10.7) as input to determine atmospheric densities and satellite drag. F10.7 has been shown to follow the sunspot number quite closely and similar prediction techniques can be used. Our predictions for F10.7 are available in a text file, as a GIF image, and as a Postscript file. Current values for F10.7 can be found at:

Now the reason why I quote the entire blog post in full is because, for some reason, Dr Hathaway won’t blog in sequential format the way normal people do, instead preferring to re-edit his previous posts.

Editing history is Orwellian, Dr Hathaway


Written by John A

July 13, 2008 at 4:53 am

Posted in Solar Cycle 24

10 Responses

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  1. If I recall correctly, this text is the prediction for SC23-maximum. The updates are meant for the graph and monthly Wolfnumbers, NOT for the SC24-prediction.

    Also, their 1999-paper only shows a prediction for SC23. No mention of SC24.

    Jan Janssens

    July 13, 2008 at 8:09 am

  2. The text is coming from the MSFC-website and is actually written for the prediction of SC23. For example, the 1999-paper only has the prediction for the SC23-amplitude.

    The update for that page is actually for indicating that the most recent monthly Wolfnumber has been added. That way, the observed versus predicted can be better tracked.

    Jan Janssens

    July 14, 2008 at 7:42 am

  3. In reading this, it sounds like he said, in essence, that these are the predictive tools we’ve developed in the past and they’ve been found to work in predicting previous solar cycles. But if the sun is behaving differently for this and the next couple of cycles, I wonder if these predictive tools will still work. For the people studying the sun, these next few decades should be most interesting.

    Leon Brozyna

    July 14, 2008 at 1:32 pm

  4. Tried posting this before; guess it didn’t take.

    Here’s an image from that’s too good to miss.

    Leon Brozyna

    July 16, 2008 at 8:17 pm

  5. YESTERDAY on the sun, three distinct magnetically active regions appeared – two (one in each hemisphere) definitely had Cycle 24 magnetic signatures (leading negative magnetic polarity in the northern hemisphere, leading positive in the south). A third area in the southern hemisphere was clearly associated with Cycle 23.

    Within less than 24 hours, the two SC24 regions were clearly fading on the magnetogram, while the SC23 region was strengthening.

    TODAY, what’s left of the two SC24 regions continue to fade away, while the SC23 region remained strong and has produced a sunspot on the visible solar disk (see the lower left quadrant of the 18 July 14:24 UTC SOHO MDI Continuum)

    A similar phenomenon happened just about one month ago (may have happened other times too that I failed to notice) – a couple of “hopeful looking” magnetic signs of Solar Cycle 24 appear, only to quickly fade away to nothing without producing a spot or “official” Active Region.

    This is probably not (as far as I know) unusual at Solar Minimum, but is another sign of SC24’s failure to get off the ground (yet).

    SC23 continues to produce spots while SC24 can’t seem to get ‘er done.

    On a (possibly) related note, the Stanford / Wilcox Observatory chart of Solar Polar Magnetic Field Strength has been updated.

    It continues to show the weakest solar polar fields since this series started in 1976.


    July 18, 2008 at 7:12 pm

  6. Following John-X, Leif, for one has been arguing that these sunspecks are indeed the sunspots we await but fail to emerge.

    Although I worry about calls for revisionism from some, I wonder if the convection cells are in fact not popping and what would that mean?

    Could a slight poloidal field be at fault?

    Gary Gulrud

    July 28, 2008 at 8:25 pm

  7. Still no one knows if this is just a normal (if somewhat long and deep) solar minimum – remember that a very deep minimum occurred in 1954, and yet was followed by the biggest solar cycle on record, #19; or if this is something more.

    The very weak polar magnetic fields today however must be a huge concern. Leif Svalgaard has shown (from work by the Babcocks) that solar polar magnetic fields were strong in the 1950s.

    Today they are the weakest ever directly observed.

    The usual model of the solar dynamo requires that magnetic field strength accumulates at the solar poles during solar minimum, where it descends and is transported toward the equator near the base of the convection zone, erupting along the way as sunspots.

    If the magnetic field strength at the poles is not there now, at solar minimum, just where are sunspots going to come from at solar maximum?

    Ken Schatten has wondered aloud whether the unusual coronal holes this minimum, especially at low latitudes, are allowing poloidal magnetic field strength to “leak” away into interplanetary space.

    I have wondered whether the sun’s “extracurricular activity,” including the largest solar flare of modern times – an X28 (estimated), part of the “Halloween Storms” of 2003 – as well as the “2nd” solar max after the official one in 2000, and the significant cycle 23 activity through the end of 2006, have also left the sun somewhat “drained” of magnetic energy for cycle 24.


    July 29, 2008 at 1:59 am

  8. There is an animated review some of Dr. Hathaway’s past predictions which were recovered from Internet cache and various dustbins across the Internet. Unfortunately Dr. Hathaway did not post new predictions for May and July 2008; it is too early for August 2008 which I am really looking forward to. Unlike previous predictions the ones for April and June 2008 are identical. Instructions for running GIF animations can be found at the bottom of this post.

    In the Hathaway animation, note that both the past and future predictions, starting at March 2008, were adjusted downward. Dr. Hathaway is not only revising the future, he is also redacting the past. If Dr. Hathaway posts an August 2008 prediction, I will update the above file.


    Directions for Viewing GIF Animations in Windows IE:

    To view the animation in IE full screen press F11.
    To return to the normal IE view press F11 a second time.
    To expand the graphic to its full size pass the pointer over graphic and right click using the magnifying class pointer with the “+” sign.
    The stop the animation press the “ESC” key.
    The restart the animation press the “F5” key.

    Michael Ronayne

    August 2, 2008 at 11:20 pm

  9. Satellite positions are described as the longitude of the place
    on the equator that the satellite hovers above. 19e means 19.2
    degrees east, which finds some Astra satellites about 35000km
    above the Congo basin, with many FTA German broadcasts.


    August 13, 2008 at 9:31 am

  10. If you think, as I do, that the current science and prediction of the sunspot cycles is somewhat ambiguous and perhaps not most reliable, why not read a new and controversial hypothesis which can be found on the website:
    Assessment from the “solar science establishment” – pure coincidence.
    My view: ‘the nature is adverse to a coincidence; it is ruled by a cause and the consequence’
    All comments welcome.


    August 16, 2008 at 6:39 pm

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