Структура и динамика полярных токовых систем : материалы международного симпозиума «Полярные геомагнитные явления», 25-31 мая, Суздаль, СССР / Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т. – Апатиты : [б. и.], 1988.

EXPERIMENTAL. Magnetic pulsation recordings used in this atudy have been collected from the north-south chain in Finland. Five stations at about the same meridian at Kevo (L н6.0), Sodankyla (L = 5.1), Oulu (L = 4.3), Jyvaskyla (L = 3.7) and Nurmijarvi (L = 3.3) have been run during the тмя (1976-1979) and afterwards. Induction coil magnetometers which have been used are most sensitive to Pel and Pi1 type magnetic pulsations. Pulsations have been recorded on magnetic tape. In one case included in the present study incoherent radar measurements of ionospheric parameters were available which provide important information especially to estimate the magnetospherio electric fields. EISCAT is a European incoherent scatter facility in the auroral aone (Folkestad et al., 1983) which has been in operation since 1981. The transmitter of the tri static radar is located at Tromstf and the remote antennas at Kiruna and Sodankyla. In the scanning mode of operation measurements can be extended to sub-auroral and polar cap latitudes. EXCITATION OF Pel PULSATIONS BY SUDDEN IMPULSES (SI). Kokubun and Oguti (1968), Troitskaya et al.(1968), Hirasawa (1981), Olson and Lee (1983) and Kangas et al.(T986) have shown several examples of Pel pulsations excited by Si's. These events occur most frequently in the n o o n - a f t e m o o n sector of the magnetosphere. 10 nT seems to be a threshold value of the SI amplitude for the generation of pulsations (Kangas et al.,1986). There is usually a delay of Hz 1.0 0.5 T •-И —г 4- , — t, ----- i 0» — ---- . . 1 06.00 KEVO 5SC 07.00 UT 27 MARCH 1977 06.00 ISSC 07.00 UT NURMIJARVI, H 27 MARCH 1977 spectra of SI associated ULF emissions observed at Kevo (L = 6.0) and Nurmijarvi (L = 3.3) on March 27, 1977. 96