Электродинамические процессы в высоких широтах: материалы междунарордного симпозиума «Полярные геомагнитные явления», 25-31 мая 1986 г., Суздаль, СССР / Междунар. геодез. и геофиз. союз, Междунар. ассоц. геомагнетизма и аэрономии ; Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т ; [редкол.: О. М. Распопов (отв. ред.). и др.]. - Апатиты : Кольский филиал АН СССР, 1988.

P.IVANOVA, P.HEHOVSKI, G.MOMCHILOV, J.Cz.MlLETIl'S SOME GEOMAGNETIC P U L SATIONS A T MIDDLE LATITUDES INTRODUCTION. D ur i n g the last years the controlling character of the solar w i n d a nd the i n terplanetary magnetic field on the pu lsation activity, indicated for the first time b y B o ls hakova a nd Troitskaya (1968), again a ttracted the atte nt i on of scientists a nd obtained a n e w experimental confir m at i o n (Troitskaya et a l .,1969,1971; Qul'elmi et al.,1973; Vero and Hollo, 1978; P o ta p o v and P o lj u s h k i n a , 1979). The close connection of the T period w i t h t h ^ M F В magnitude and of the amplitudes (or the frequencies of o ccure nce) w i t h the solar w i n d velo o lt y V 0W a n d angle V b e t we e n В and the line Sun-Earth is well established (see e.g. Greenstadt et al.,1983i R u s s e l l ,1983; Vero et al.,1985, Yumoto et al.,1985). I n spite of the huge experimental material the mechanisms responsible for the occurence of pulsations at middle latitudes are not yet clarified (Vero et al.,1985)* The hypothesi'a of i ni t iating these pulsations in the r e gi o n of the b o w shock wave b y the r e flected protons ( G u l 'elmi,1974) and their subsequent pe ne t r at i o n t hr ough the m a g n e t o s h e a t h , magnetosphere a nd to the E a r t h at middle latitudes, is proposed as the most plausible one. W i t h i n the framework of this conception, however, a series of facts cannot be exp lained, w h i c h re f e r to the p e riod dependence on the geomagnetic latitude ( Miletits,1980), of the amplitude on the substorm acti v i ty (Vero et al.,1985} Irrespective of the fact that the connection of the pulsations parameters wit h the substorm a ct i v it y is obvious (it is of complicates character) bot h by Kp a nd V ^ . i t is not directly connected w i t h the m e ch a n is m of the pulsa tions excitation. I n the present study on the basis of the data on the g e oe l ectric pulsations fr o m a ne a r l y ope m o n t h period, a n attempt has be e n made to investigate the dependence and mechanisms connecting the amplitudes w i t h the geomagnetic activity. To this end instead of the Kp index we use the D at index which, on the one hand, characterizes the dynamics in the region of the ring current properly and, on the other hand, can come close to the r eg i o n of plasmapaцре, where one of the maxima of the pulsations amplitude distribution is (Chen arid Hasegava,1974; S o u t h wo o d ,1974). E X PE R I M EN T A L BASIS. B y a KAP G project in 1984 a joint Bu l g arian-Hunga- ri a n expedition w a s carried out on the territory of the People's Republic of Bulgaria (Preselentsi) measu r i ng the geoelectric pulsations for the time p e riod 10.09.1984-10.10.1984. The m ea surements wer e made by means of Hung a r ia n instruments, identical to those used in Hungary, wh i ch ensured the po s sibi lity for a comparison of the obtained records. T^e pulsation records were mad e w i t h a sensitivity 0.3-0,6 m V / k m / m m a n d 1 m i n / 6 m m - horizontal scale. We examined events w h i c h are at least about twenty minutes long and have some pulsation activity. We dividedttiem into the following classes: 1 ) oscillations (very re g ular mono-harmonic pulsations); I02