ON THE CLAIMED 5.5-YEAR PERIODICITY IN SOLAR-ACTIVITY

Recently, Djurovic and Paquet (1996) claimed to have found an oscillat ion with a period of about 5.5 years in several solar and solar-terres trial parameters. in particular in solar activity as indicated by suns pot numbers. Since the temporal evolution of the solar activity and so lar-terrestrial environment is of great interest in many fields, we ha ve examined their claim in detail. We show here that their conclusion is based on an artefact due a questionable method applied, and due to the asymmetric form of the solar cycle. Accordingly, there is no reaso nable evidence for the existence of a fundamental 5.5-year periodicity in solar activity.