On the green corona variability as reported by four groups of observers - an attempt of comparison

We have compared four published databases of monthly means of the whole disc green coronal brightness (Fe XIV, 530.3 nm line) which cover the long period of about five last solar cycles. They are from the Norikura Observatory (1) prepared by Sakurai et al (1999), Kislovodsk Observatory (2) reported by Makarov et al. (2003), intensities registered by several coronographs and converted to the common photometrical scale of Pic du Midi (3) by Kulcar et al. (1991) and Sykora (1992), intensities from several observatories converted to the photometric scale of Lomnicky Stit (4) and published in the form of coronal index by Rybansky & Rusin (2001). As the solar corona is the source of the solar wind a fundamental question appears: which of these data set render well the real variability of the corona? We studied the variability of these data by means of correlative, regression and variance analyses between the data and the other solar indices as sunspot number, area of sunspots and Ottawa radio flux data. These analyses and tests used show that variability of the data sets (2) and (3) are nearing to the pair of the solar indices: sunspot numbers and radio flux. All studied databases demonstrate the better agreement during periods of minimal and moderate activity.