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N-S Asymmetry of the Solar Activity – Area of Polar Coronal Holes and Chromospheric Plages

Authors: Dorotovič I. and Journoud P.

Ref.: Proceedings XIV Encontro Nacional de Astronomia e Astrofísica, Angra do Heroísmo, Terceira, Açores, Portugal, 22 – 23 July 2004 (published on CD), published on CD (2004)

Abstract: It is well know that the level of the solar activity in the northern and the southern hemisphere is not uniform. This fact is confirmed by long-term observations of various solar indices and it seems that the north-south (N-S) asymmetry is a specific independent and very promising tool for analysis of the long-term solar activity variations. N-S asymmetry of polar coronal holes size over the period 1939-1996 has been investigated in the paper. Daily values of the area of polar coronal holes as estimated from the green coronal line intensities were used as an input of the investigation. The analysis revealed that the south asymmetry dominated during the studied period. A software tool to estimate the N-S asymmetry from the area of the chromospheric plages (as derived from the Ca II K3 spectroheliograms taken in the Observatório Astronómico da Universidade de Coimbra) is presented as well.