Resolution No.13 (1963): Classification of pulsations

On account of experimental knowledge obtained since the IGY, the IAGA recognises the need of improving the present classification of pulsations. Pulsations fall into two main classes: those of a regular, and mainly continuous character, and those with an irregular pattern. The first class, for which the name pc is retained, covers the whole range of pulsations (0.2-600 sec). This class is provisionally divided into five subgroups:

• pc 1: 0.2 to 5 sec
• pc 2: 5 to 10 sec
• pc 3: 10 to 45 sec
• pc 4: 45 to 150 sec
• pc 5: 150 to 600 sec

The second class of pulsations is characterised by their irregular form, their close connection with disturbances of the magnetic field and their correlation with upper atmospheric phenomena. This class provisionally is divided into two subgroups covering different frequency ranges:

• pi 1: 1 to 40 sec
• pi 2: (primarily pt) 40 to 150 sec

Observatories making such analyses are strongly urged to take into account the classification given above, which will be circulated with more details by the working group on Morphology of Rapid Variations of Commission No. 4.