COMMENTS ON THE INDICES OF THE SOLAR ACTIVITY AND ITS ELEVEN-YEAR CYCLE VARIATION

Abstract

The pattern of the eleven-year variation of the relative sunspot numbers, i.e., the Wolf numbers, is much different from that of the solar flares associated with the emissions of solar cosmic rays, type IV and great microwave impulsive radio bursts. Roughly speaking, the maximum phase of the latter is later by about three years from that of the former. It seems that such a time delay has been brought by the use of the relative sunspot numbers as the index of solar activity. Taking into account that the occurrence frequency of solar flares is approximately proportional to the relative sunspot numbers, the degree of solar activity related to the active phenomena on the sun is inferred to be closely connected with some of the nature of sunspots and their groups. It is clear, furthermore, that the pattern of the eleven-year variation of the coronal brightness with respect to the 5303A green line emission is very similar to that of the occurrence frequency of solar cosmic-ray flares. This fact suggests that the occurrence of solar cosmic-ray flares is connected with the coronal active regions. Some critical discussion is given on the indices of solar activity from the view points that the coronal activity is intimately connected with the active phenomena over the sun's photosphere. It is shown that the relative sunspot numbers in each of the northern and southern hemispheres must be defined as the representative index of solar activity, whenever the relative sunspot numbers are adopted.