AURORAL TORCH STRUCTURES - RESULTS OF OPTICAL OBSERVATIONS

Auroral torch structures are frequently observed as large scale wave-l ike undulations on the poleward edge of the diffuse precipitation zone . Their eastward drift velocity has the same order of magnitude and di rection as the electric drift velocity usually observed in the morning sector. From a study of all-sky camera and TV data, the main peculiar ities of the torch structures are shown. Three cases were studied. Hei ght distributions of luminosity along the boundaries of the torch were made using the triangulation method in the first case. It was shown t hat the poleward boundary of the torch had the lowest altitudes around the crest. The second case was the appearance of a train consisting o f five torches that existed for a relatively long time (approximately 20 min), drifting eastward. On the contrary the last case was the succ essive development of two torches recorded by the TV camera. For the t wo latter cases the field-aligned mapping of the torches into the magn etotail is made using the latest version of the Tsyganenko magnetic fi eld model (1989). The results of mapping showed that the generation of torch structures takes place quite close to the Earth, at a distance of 5-6 R(E).