Can One Predict Sunspot Numbers?

(And where can one get the latest sunspot numbers?)

(by Amara Graps)

Daily Sunspot Numbers

To find the sunspot numbers, you can go to the Sunspot Index Data Center (SIDC) in Belgium, which is the world data center for sunspot index of daily sunspot numbers.

At their center they collect data from all of the stations, compare, average, weight, etc. and then make the sunspot numbers available at the beginning of every month.

Predicting Sunspot Numbers

According to Todd Hoeksema (Stanford), sunspots appear randomly within the envelope of the solar cycle, and they typically live about a month. One knows the rate with which they will appear to produce the expected number of sunspots, but you can't really predict when the next one will appear. Each sunspot cycle is different and there's no reliable way to make a prediction.

The magnetized realm in, around and above bipolar sunspot groups is a disturbed area called a solar active region (Lang, 1995, pg. 85). Active regions are a place of concentrated, enhanced magnetic fields, a collection of intense magnetic loops. They together form a magnetic sphere of influence, in which the strong magnetism dominates the motion of chaprged particles in its vicinity.

Active regions begin their life when magnetic loops emerge from inside of the Sun (Lang, 1995, pg. 85) . The magnetic structure of an active region then gradually changes in appearance as new magnetic loops rise to the surface and its sunspots move and shift about. Eventually, the active regions simply disappear- over the course of weeks to months, their magnetic loops break apart, disintegrate, or submerge back inside of the Sun.

Solar scientists are very much interested in forecasting active magnetic disturbances, in particular, the flares that arise out of active regions. They run complex code that models the magnetic field of the Sun. But it is very much like weather forecasting, an imprecise science. So they can give probabilities, based on their model results, only.

You can get a daily forcast for magnetic disturbances from NOAA:
and (more detailed).

You may wish to browse more around their site. They have an elaborate website that describes all aspects of their work (You may find a description of their techniques used in forecasting, for example).

You may also be interested in some "Basic Facts about Sunspots" giving very nice explanations and diagrams describing how sunspots are thought to form.

And finally, for an interesting perspective on sunspot number versus human technological advance, you can click here.


Lang, Kenneth, _Sun, Earth and Sky_, Springer Verlag, 1995.

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Special Thanks to A. Graps.