Longitudinal distribution of flares in the late phase of active regions

Abstract

For solar cycles 20 and 21, the longitudinal distribution of the D, G, and H-type solar flares which are related to the final phases of active region evolution, have been analysed for the northern and the southern hemispheres separately. One active zone has been found for D, G, and H-type flares, and one more active zone has been found for the H-type flares of the northern hemisphere for cycle 20. Two active zones have been found for the D and H-type flares of the northern hemisphere for cycle 21. Southern-hemisphere flares are concentrated in two active zones for cycle 20. The active zone in the northern hemisphere, which rotates with a synodic period of about 26.73 days, produced 30% of the examined D-type flares during cycle 20 and persisted in the same position during the two solar cycles, 20 and 21. The active zone in the southern hemisphere rotated with a synodic period of about 27.99 days. Only the active zone producing D-type flares persisted in the same position during the two solar cycles.