Occurrence and recurrence in auroral activity in DMSP images

摘要: We rated the auroral activity in 749 southern hemisphere DMSP images taken during 1972 and 1973 on a qualitative scale with active (A), moderate (M), quiet (Q), no aurora (N) categories. The overall occurrence rates of A, M, Q, N ratings are 0.17, 0.55, 0.16, 0.11, respectively. After one orbit (102 min), both A Q conditions recur about half cases. Thus successive showing occur more often than expected from images. difference between recurrence rate M is much smaller (0.63 versus 0.55), suggesting that activity, as seen series images, occurs essentially randomly. Nearly random, short-period (15–30 min) bursts have been observed by Krukonis Whalen (1980) montages all-sky photographs 1 min apart. Our results, which cover longer time span, consistent this behavior confirm scales differ full duration classic substorm pattern.