Abstract. Using the method of characteristics to invert ground-based data of the ground magnetic ®eld disturbance and of the ionospheric electric ®eld, we obtain spatial distributions of ionospheric conductances, currents, and ®eld-aligned currents (FACs) associated with a north-south auroral form that drifts westwards over northern Scandinavia around 2200 UT on December 2, 1977. This auroral form is one in a sequence of such north-south structures observed by all-sky cameras, and appears 14 min after the last of several breakups during that extremely disturbed night. Our analysis shows that the ionospheric Hall conductance reaches values above 200 S in the center of the form, and upward¯owing FACs of up to 25 lA/m 2 are concentrated near its westward and equatorward edge. The strong upward owing FACs are fed by an area of more distributed, but still very strong downward-¯owing FACs northeastward of the auroral form. In contrast to the conductances, the electric ®eld is only slightly a ected by the passage of the form. We point out similarities and di erences of our observations and results to previously reported observations and models of`auroral ®ngers', north-south aurora', and`auroral streamers' which are suggested to be ionospheric manifestations of bursty bulk¯ows in the plasma sheet.
Results are presented of observations of arti cial optical effects in the atmosphere that were made mainly by means of all-sky cameras in northwest Russia and Scandinavia. There were six arti cial optical effects observed during 10 years of observations made simultaneously from two or three stations and ve more from single stations. One of the cases was registered by a television camera on Heiss Island (Frantz-Joseph Land), and these observations allowed assumptions to be made on the volumetrical shape of the phenomena. It was assumed to have a toruslike form rather than a spherical shape, and the luminosity was caused by Rayleigh scattering of sunlight by particles, which formed a gas and dust cloud during the launch of a rocket. Observations from distant points were used to make triangulationmeasurements. It was shown that all of the observed phenomena had both common and original features. The altitudes of luminosity for different cases varied from 230 to 1080 km. The clouds represented rapid horizontally expanding circular objects with the front edge propagation velocity of 3-7 km ¢ s ¡ 1 . Diametrical sizes of luminous clouds in some cases exceeded 1600 km at later stages of their development. Five of the six phenomena, the sizes of which were measured by triangulation, were most likely caused by launches from the Plesetsk rocket range in northwest Russia, whereas the remaining one apparently was launched from a place located in west of the Kazakh republic. The possibility of observations of such types of phenomena depends very much on sunlight conditions, direction of launch trajectory, and weather conditions.
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