North-South Distribution of Solar Flares during Cycle 23.pdf

a r X i v : a s t r o - p h / 0 5 0 8 5 3 9 v 2 2 9 N o v 2 0 0 5 J. Astrophys. Astr. (0000) 00, 000–000 North-South Distribution of Solar Flares during Cycle 23 Bhuwan Joshi ? 1 , P. Pant 1 and P. K. Manoharan 2 1 Aryabhatta Research Institute of Observational Sciences, Nainital 263 129, India 2 Radio Astronomy Centre, TIFR, Ooty 643 001, India 2008 February 5 Abstract. In this paper, we investigate the spatial distribution of solar flares in the northern and southern hemisphere of the Sun that occurred during the period 1996 to 2003. This period of investigation includes the ascending phase, the maximum and part of descending phase of solar cycle 23. It is revealed that the flare activity during this cycle is low compared to previous solar cycle, indicating the violation of Gnevyshev-Ohl rule. The distribution of flares with respect to helio- graphic latitudes shows a significant asymmetry between northern and southern hemisphere which is maximum during the minimum phase of the solar cycle. The present study indicates that the activity domi- nates the northern hemisphere in general during the rising phase of the cycle (1997-2000). The dominance of northern hemisphere is shifted towards the southern hemisphere after the solar maximum in 2000 and remained there in the successive years. Although the annual variations in the asymmetry time series during cycle 23 are quite different from cycle 22, they are comparable to cycle 21. Key words: Sun: activity – Sun: flares – Sun: North-south asymmetry 1. Introduction The distribution of various solar activity features with respect to heliographic lati- tudes as a function of time has been investigated in several studies. These activity features include flares, filaments, magnetic flux, sunspot numbers, sunspot area etc. These studies indicate that a solar cycle is not symmetric considering the distribu- tion of solar activity separately in northern and southern hemisphere. This intrinsic feature (N-S asymmetry) poses a