The Wolf number ( “international number of sunspots” , “relative number of sunspots” , “Zurich number” ) is a numerical indicator of solar activity associated with the number of sunspots . Named after the Swiss astronomer Rudolf Wolf . It is one of the most common indicators of solar activity. Popular in all sorts of meteorological forecasts.
The Wolf number W for a given day is calculated by the formula
where f is the number of observed spots;
- g is the number of observed groups of spots;
- k - normalization factor .
The normalization coefficients k are derived for each observer and telescope , which makes it possible to share the Wolf numbers found by different observers. For the international system, the Wolf numbers were taken, which in 1849 began to publish the Zurich Observatory , and for which the coefficient k was assumed equal to 1. Currently, all observations of sunspots and the determination of monthly and annual average values of the Wolf numbers are made in the Center for Analysis of the Effects of the Sun ( Belgium) . There are also series of Wolf numbers reconstructed from indirect data for the epoch preceding 1849.
The Swiss astronomer M. Waldmayer [1] obtained the following empirical relationship between the average annual values of the Wolf number and the total area of sunspots:
where F is the area of spots in ppm hemispheres. However, there are a number of indications [2] to change the nature of this relationship with time.
See also
- Solar cycling
- Eleven year solar cycle
- Maunder minimum
Notes
- ↑ Waldmeier M. Ergebnisse und Probleme der Sonnenforschung. 2 Auflage, Leipzig, 1955.
- ↑ See. Vitinsky Yu. I. , Kopetsky M., Kuklin G.V. Statistics of sunspot-formation activity of the Sun. - M .: Science, 1986. - 201 p.