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Paper: North-South Asymmetry of CaIIK Plages
Volume: 368, The Physics of Chromospheric Plasmas
Page: 527
Authors: Dorotovic, I.; Journoud, P.; Rybak, J.; Sykora, J.
Abstract: The level and evolution of solar activity is not identical in the northern and southern Sun’s hemispheres. This fact was repeatedly confirmed in the past by analysis of a number of long-term observations of various solar activity indices. Presently, it seems that the north-south (N–S) asymmetry represents quite specific, independent and very promising tool to advance in analysis of the long-term solar activity variations. This paper is focused to give a software tool for estimation of the N–S asymmetry in the area of bright chromospheric plages, as measured on the Ca IIK3 spectroheliograms registered since 1926 in the Observatório Astronómico da Universidade de Coimbra, Portugal. In fact, studies of the N-S asymmetry of just this phenomenon are rare, namely due to absence of technique allowing reliable quantitative estimations of the Ca IIK3 plages parameters. Our algorithm is also partially limited, it provides the area of bright Ca IIK3 emission structures, but it does not perceive differences in the brightness of individual chromospheric features. As for the N–S asymmetry of the chromospheric plages alone, we present here a sample of its estimation only. Its behavior during the first half of 2000 year is provided to illustrate application of the software developed. A comparison and cross-correlation with the N-S asymmetries found for the sunspots and corona green line brightness is added. We intend to discuss the results of more extensive analysis of the chromospheric plages N-S asymmetry as soon as a sufficiently long time series of the Ca IIK3 Coimbra spectroheliograms will be digitized and processed.
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