Indices for the epochs of the solar activity minima

4. Index of the Number of Bright Points in the Ca II K Line

Figure 5

[15] The daily Ca II K spectroheliograms of the full solar disk were processed by using the photo archive of the Kodaikanal observatory (India) for the time period from 1907 to 1995. It has been shown that the 11-year cycles of the Ca II K index at the latitudes of sunspot formation coincide with the cycles of Wolf numbers and radio emission with a wavelength of 10.7 cm [Tlatov and Makarov, 2004]. On the other hand, the Ca II K bright points at high latitudes form polar cycles between the epochs of the magnetic field sign reversal. It has been found that the polar cycles of the Ca II K bright point areas at high latitudes ( S_K ) precede, on the average, by 5-6 years the 11-year cycles of Wolf numbers (Figure 5).