Sunspot Relative Numbers and Solar Activity Reports

Sunspot Relative Numbers

Sunspot Numbers are valuable for a rough characterization of Solar Activity. Although the physical meaning is limited they show a good correlation with other physical parameters of Solar Activity. The derivation is very simple and so long timeseries are available.

Solar Activity Reports

Solar Activity Reports of Kanzelhöhe Observatory add a short characterisation of the solar activity - like dominating sunspot groups or flare activity - in textual form to the usual monthly tables of sunspot relative numbers. These reports are available since 1969.

Provisional Sunspot Relative Numbers

The provisional sunspot relative numbers are derived from the daily sunspot drawings. For this purpose the solar disk is projected with a diameter of 25 cm onto a drawing desk. The also called Zürich Number or Wolf Number R is calculated

k...Correction factor (which depends on the actual seeing conditions and the used instrument) to make observations from different places comparable

g...Number of sunspot groups

f...Number of spots (umbrae) observed

Sunspot relative numbers observed at Kanzelhöhe Observatory since 1944.

Definitive Sunspot Relative Numbers

The provisional numbers are compiled and reported monthly to the Solar Influences Data analysis Center (SIDC) at Brussels. Contributions of several observing stations are averaged in an advanced form and published as definitive sunspot numbers.