An Estimation of the Long-Term Variation of a North–South Asymmetry of the Long-Lived Solar Filaments

The present paper estimates the long-term variation of the north-south asymmetry of long-lived solar filaments from Meudon's catalogues during the period 1919–1989. A long-time period of the filament asymmetry variation of about 11 solar cycles was found by using the cumulative index for the filament north-south asymmetry. This estimation is very close to the long-time variation period of the north-south asymmetry of solar activity obtained by means of a spectral analysis.