The INTER-SOL Programme (ISP)

Examples (1):
Registration of sun spots

A single spot without any penumbra
(not belonging to any group!)

A single penumbral spot
(not belonging to any group!)

A spot group with penumbral
and non-penumbral spots

A spot group with penumbral
spots only

Special tips for classifying spot groups

The classification of spot groups according to the Waldmeier principle may be difficult in times of high activity, especially if many groups are grouped together or form complex structures. Some simple rules can be applied here:

• Spots within an area of 5°x5° on the sun can be classified as a group if no bipolar structure is visible. Bipolar groups on the other hand can reach lengths of 20° and more.

• Two single spots with a separation of up to 15° solar longitude can be classified as one group if they are the remains of a previous larger group.

• A bipolar accumulation of spots can be classified as a group if the westerly part appears at the same or lower latitude than its easterly part. The inclination of the longitudinal axis of a group at or around +/- 10° solar latitude can amount to 1 - 2° whereby the inclination of a group at or around +/- 30° latitude can be up to 4°. [H. Künzel, Astronomie und Raumfahrt 14, 121 (1976)]
  

Please note:  A single spot is, contrary to the common counting methods, not (!) regarded as a group in the INTER-SOL Programme.

Please do also have a look at the Fundamentals Page!