Numerical expression of sunspot activity

Data for the graphics are taken from home made observations.

Updated: May 2020

The Wolf Sunspot number R

It was introduced by Rudolf Wolf in 1848. Determining Wolf numbers is a favorite amateur observing program as it can easily be performed using small telescopes.The Wolf sunspot number includes the number of observed single spots s as well as that of the entire spot groups g. Wolf multiplied the number g of groups with a factor 10 in order to express the fact that the appearance of a new group is weighted 10 times higher than a new spot within an existing group.An isolated spot is regarded as a separate group. The Wolf number R is combined from spot and group numbers according to the relation:

R = 10g+s

The new sunspot number after Beck R

When the observer determines the spot number and the Waldmeier class of a group he/she can estimate the area of the group by multiplying the spotnumber S with a weight factor G, representing the average area/number ratio for the group type.The new area number R is obtained by adding the area numbers of all groups.
The following weight factors G for the Waldmeiers classes are used:

Waldmeier class = A , B , C , D , E , F , G , H , J.
Weight factor G = 4 , 4 , 8 , 18 , 25 , 36 , 50 , 44 , 37.

The Classification Value after Malde CV

Introduced by the Norwegian Astronomical Society. The system is based on the McIntosh Spot Classification which admits 60 possible classes.These are arranged in a sequence giving the highest weight(60) to an F-group with large symmetric penumbra and with complex spot distribution. A single A-spot is assigneda CV-weight of 1. The CV-valuesof all groups are added and thus form the measure of spot activity.

The Pettisindex SN

Another sunspot number, one which considers the formation of penumbrae as signs of high solar activity.The Pettisindex is defined as:

SN = 10p+s

Where p is the number op spots with penumbrae and s that of spots without penumbra. A penumbra with more than one umbra within it,is counted as p =1.

The Paderborn Intersol index IS

In 1976, the Astronomische Arbeitsgemeinschaft Paderborn proposed a different Wolf number. The Paderborn sunspot number IS defined as:

IS= gr+grfp+grf+efp+ef.

gr - number of spot groups (consisting of two or more spots)
grfp - number of penumbral spots belonging to a group (each umbra within one
penumbra is to be counted as "grfp")
grf - number of spots without penumbra belonging to a group
efp - number of single penumbral spots being no members of any group
ef - number of single spots without penumbra being no members of any group

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