Hot Spots for Solar Activity

Abstract

Studies on hot spots and active longitudes are briefly reviewed in this paper. Although the concept of active longitudes are old, interesting discoveries were made by recent studies, which applied new analysis methods to data covering several solar cycles. The main characteristics of hot spots are as follows: (1) Hot spots, initially recognized as areas where major flares erupt preferentially, are also preferred areas for emergence of big sunspot groups. (2) Double hot spots appear in pairs that rotate at the same rates, separated by about 180° in longitude. Single hot spots have no such companions. (3) The northern and southern hemispheres behave differently in organizing solar activity in longitude. Because of this north-south asymmetry, the areas for preferred flare eruptions are called hot spots (Bai 1987). (4) Lifetimes of hot spots range from one to several solar cycles. (5) A hot spot is not always active throughout its lifetime but goes through dormant periods. (6) Hot spots with different rotation periods can co-exist in the same hemisphere during the same solar cycle.