%0 Article %A V. Safargaleev %I Copernicus Publications %D 1997 %G English %B Annales Geophysicae %@ 0992-7689 %@ 1432-0576 %T Luminosity variations in several parallel auroral arcs before auroral breakup %U https://www.ann-geophys.net/15/959/1997/angeo-15-959-1997.pdf %X Variation of the luminosity in two parallel auroral arcs before auroral breakup has been studied by using digitised TV-data with high temporal and spatial resolution. The intervals when a new arc appears near already existing one were chosen for analysis. It is shown, for all cases, that the appearance of a new arc is accompanied by fading or disappearance of another arc. We have named these events out-of-phase events, OP. Another type of luminosity variation is characterised by almost simultaneous enhancement of intensity in the both arcs (in-phase event, IP). The characteristic time of IP events is 10–20 s, whereas OP events last about one minute. Sometimes out-of-phase events begin as IP events. The possible mechanisms for OP and IP events are discussed.