Полярные геомагнитные возмущения и связанные с ними явления : материалы международного симпозиума «Полярные геомагнитные явления», 25-31 мая 1986 г., Суздаль / Междунар. геодез. и геофиз. союз, междунар. ассоциация геомагнетизма и аэрономии, АН СССР, КНЦ, ПГИ. – Апатиты : [б. и.], 1989.

Evidently, it corresponds to a space leap of plasma and/or geomagnetic para meters w h i c h define the mec h a n i s m of precipitation. R E F E R E N C E S 1. A KASOFU S . - I . A study of auroral displays photographed f r o m the DMSP-2 satellite and f r o m Alaska m e r i d i a n ch a i n of stations. - Space Sci. Rev., 1974, v.16, p-617-725. 2. ANDRE D . , BAUMJOHANIT W. Joint two-dimensional observations of ground magnetic an d ionospheric electric fields a s s ociated w i t h auroral currents. 5. Current system a s s o ciated w i t h eastward d rifting omega bands. - J.Geophy3. 1982, v.50, p . 194-201. 3. GUSTAFSSON G . , BAUMJOHANN W . , IVERSEN X. M u l t i-method observations and m o deling of the three dimensional currents associated with ve r y strong P s6 event. - J.Geophys., 19B1, v.49, p . 138-145. 4. OGUTI Т., K OKUBUN S., H AXASHI K . , TSU R U D A K., MACHIDA S., KI TAMARA T. SAKA 0., W ATANABE T. A n auroral to r c h structure as a n activity center of pulsating auroras. - Can.J.Phys., 19B1, v.59, p . 1056-1062. 5. RE E S M.H. A uroral i o n i zation and excitation by incident energetic eleotrons. - Planet.Space Sci., 1963, v.11, p . 1209-1218. 6. Tagirov V . R . , T r a k h t engerts V . Y u . , C h e m o u s a S.A. On the nature of p ulsating auroral patches. 1. Experimental data. - Preprint P G I - 8 5 - 0 3 - 4 I , Apatity, 1985, 38 p. (in Russian). T.A,Kornilova, S.A.Chernouss, M.X. P u d o v k i n BLACK AURORAS Auroras having a n increased l u m inosity against the b a c kground is concid- ered ordinary. But al o n g wi t h this phenomenon there exists the so called black aurora whose luminosity is decreased as c ompared wi t h the surrounding background /1-5/. A particular peculiarity of black aurora is the existence of dark s t r u c tures within diffuse luminosity. Such structures are ve r y often short-living w i t h the forms res e m b l i n g ordinary auroras. The present w o r k is aimed at c l a s sifyi ng this phe n o m e n o n on the basis of TV data a n d defining its physical mechanism. The TV data of black auroras obtained at Apatity in Fe b r u a r y 1981 and Mar c h - A p r i l 1984 have be e n used. The analysis of the TV r e c o rdings indicates that there are three types of black auroras. They arei a) bl a c k auroras ap p e a r i n g against the quiet diffuse back ground between ordinary a uroral bursts. They are in temporal coincidence w i t h positive peaks on the general negative ma g n e t i c disturbance (I'ig.1). B l a c k auroras of this type can be treated as a time b o r d e r between ordinary auroral burstsi their life-time is 10-20 minutes, b) B l a c k auroras existing simultaneously w i t h active o r dinary auroras an d in their vicinity. Sometimes auroras f orming the spatial border dividing diffuse l u m inosity an d active auroras were observed, c) B l a c k pulsating au r o r a s e x isting simultaneously w i t h pulsating o rdinary auroras (arcs or spots)* d u r a t i o n of the pulsating process is r e l atively l o n g (10-20 minutes) an d forms a n integral pulsating process w i t h ordinary auroras. Black auroral forms are just the same aa these of ordinary auroras such as arcs, bands, curia, patches, fold structures. B l a c k arcs and bands (Fig.2) are moat often observed i n c o m parison with other forms. 91