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.

Sometimes the luminosity irregularities are observed w i t h i n the background luminosity in the vicinity of black bands. Th e y are either u nmoving or move very slowly (from a few h u n d re d m/e to 1-5 km/s). She velocity is m u c h hi g h e r near the bands existing during active aurora ( ~ 10 km/s). The black bands inner structure m a y be a vo r t e x type of quasi-periodical spatial strua- ture spreading along the b a n d (Fig. 2). The curl r o tation i n the b l a c k bands were clockwise if viewed against the magnetic field lines,i.e. opposite to the r o tation of curls i n ordinary a u r o r a . Still an o t h e r type of black bands axe those forming a spatial border separating diffe* rent auroral types, e.g. between diffuse and model of the V-shaped double aotive ^ « ^ t e aurorae, pulsating a n d n o npuls- layer in the outer iono- ating ones. sphere. o n morphological features of bl a c k auroras indicate that these aurorae are not just a gap be t w e e n two diffuse auroral regions. It i s a p h e nomenon m u c h like ordinary auroras. A c c o r ding to m o d e r n conceptions (see for example /6/) the usual discrete aurora ia re l ated to elec t ron b e a m a c c e l eration i n a double potential layer of the V-shape w i t h the E - e lectric field directed upward. It is natural to suppose that the bl a c k aurora is a result of a strong d e c e l eration of auroral elect rons in the same double layer w i t h the eleotric field be i n g directed down w a r d (Pig. 4). If this is really so one should expect a n umber of characteris tic features r elated wife the existence of au o h a double layer. They can be the following. 1. A n auroral p r o t o n b e a m a c c e l eration toward the B a r t h and, as a result the appearance of h y d r o g e n emi s s i o n i n the b l a c k aurora a n d nearby. 2. For m a t i o n of a trough in the auroral ele c t r o n energetic spectra in an energy range of some keV. 3. Typical movement of the b a c k ground i n h o m o g eneities along the black arc. This movement is d i rected f r o m west to east an d f r o m east to west in the regions southward a n d n o r t h w a r d f r o m the b l a c k arc, respectively. A detailed analysis of bl a c k aurora spectrograms ha s gi v e n a possibility to distinguish h y d r o g e n e mission in the spatial ionosphere r e g i o n with bl a c k auroras. As fo r the second feature we m a y state that the satellite of "Oreol" type do fi x the r e g i o n w i t h softening of p e r c i p itating electron energetic spectrum. The analysis of m o v e m e n t s of l u m inosity inhoraogeneitiee w i t h i n the TV camera v i e w in the v i c i n i t y of a bl a c k b a n d h a s be e n performed to testify the third feature. Unfortunately, there were o n l y f e w cases w h e n a single arc was w i t h i n the TV camera f i e l d of view. Nevertheless, the movement of luminosity inhomogeneities wa s dis t i n c t l y observed b e i n g directed fr o m west to east s outhward of the arc, i.e. parallel to the arc w i t h a velocity of 1-5 km/s. The diffuse b a c k ground lum i n o s i t y n o r t h w a r d of the arc (band) seemed so h o m o geneous that it wa s h a r d l y possible to deteot luminous inhomogeneitiee. In Fig, 4. Equipotential 93