Solar cycle variation of coronal green line index

Abstract

<span style="font-size:11.0pt;mso-bidi-font-size: 10.0pt;font-family:" times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";="" mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-GB">During 1966-2008 (solar cycles 20-23), the evolutions of sunspots (Rz) and solar flare index (SF) show similar evolution, i.e. a rising phase, a broad maximum and a declining phase in each cycle. On the other hand, coronal holes are more frequent in the declining phase of each cycle. Hence, the coronal green line index (CG), which represents coronal heating, is expected to be similar to sunspots and solar flare index during the rising and maximum phases of solar cycle but dissimilar in the declining phase. Observations show that this was true, but the excess of CG in the declining phase is small compared to the CG intensities at solar maximum. Thus, the contribution of coronal hole could not be unique or even major one for the large coronal heating. There are many solar parameters which evolve differently from the sunspot numbers. But in the present paper, it is assumed that comparison with sunspot numbers may be a reasonable one.</span>