Evidence for solar-cycle evolution of north-south flare asymmetry during cycles 20 and 21

摘要: The record of flare incidence from January 1969 to October 1988 indicates that the north-south (N-S) distribution large flares is periodic and approximately in phase with 11-year sunspot cycle. These data are based on observations whole-disk Sun continuum soft X-rays which commenced early have proceeded without interruption present time. pattern occurrence, observed for slightly less than two cycles, concentrate north heliographic latitudes soon after solar minimum then migrate gradually southward as cycle progresses. By end cycle, most occur south. degree N-S asymmetry apparently a function intensity flare; intense show largest amount asymmetry. suggest sunspots may be driven by distinctly different excitation mechanisms arising at levels convection zone. This conjecture supported recent work Bai (1987, 1988), who has discovered superactive regions producing majority rotate speed substantially Carrington rate, primarily motion sunspots.