A comparative study of solar facula during cycle 23 and 24

Abstract:

The solar activity minimum between the end of cycle 23 and beginning of cycle 24 was the longest and deepest since the modern satellite era of 20th century. In this paper, we have investigated statistical properties of solar facula and sunspot area (and their ratio) covering entire solar cycle 23 and the ascending phase of cycle 24. The facular area has been considered from the K-line composite at the San Fernando Observatory and is a direct measurement of the strength of solar cycle activity. It is found that solar facular area decreased during minimum phase of cycle 23/24 compared to maximum phase and also during rising phase of cycle 24. However, the ratio of facula to sunspot area increased during minimum epoch of cycle 23. Power spectrum analysis shows that along with other periods, the solar rotational periods 22 -31 days and Rieger type periods are both prominent during maxima, minima of cycle 23 and ascending branch of cycle 24. During the decline phase of cycle 23, the period ~ 27 days is more prominent whereas ~ 14 days and ~ 31 days periods are dominant during activity maxima. During maximum phase of cycle 23 and 24, there was no phase lag between sunspot and facular area, but a phase lag ~ 3 months has been detected during activity minima of cycle 23. These results indicate that the distribution of active regions during the activity maximum years is quite different from that in the minimum years. We shall present discussion of our results in this paper.