Statistical properties of Hα flares in relation to sunspots and active regions in the cycle 23

The statistical properties of Hα flare occurrences compared with those of sunspot and active region areas in the cycle 23. The flare numbers in the cycle 23 of all significances and locations were obtained from the Solar Geophysical Data (SGD) and the other data were taken from the automated Solar Feature Catalogues (SFC, http://solar.inf.brad.ac.uk). The average monthly flare occurrences during the whole cycle correlate closely with the total and cumulative areas of active regions and sunspots. The cumulative distribution of solar flare occurrences at different latitudes in the northern and southern hemispheres versus the time reveal a strong asymmetry with a domination of one or other hemispheres similar to the cumulative distributions of sunspots and active regions. Although the sunspot area asymmetry lags the flare occurrence asymmetry by about a few months at the ascending phase of the cycle and up to 12 months in the descending one. The latitudinal distribution of flare occurrences in the whole period reveals a well defined maximum at 18° in the northern and two maxima at 14° and 20° in the southern hemisphere. The longitudinal distributions of flare occurrence residuals of the running values and those averaged with a one year filter reveal a set of persistent longitudes in the opposite hemispheres lasting for about 1.0-1.5 years and changing quickly a few times over the cycle phases. © 2009 Elsevier Ltd