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.

о А/ О/ О/ 01 01 INCREMENTAL 015 ois 015 О й 015 ABSORPTION(dB/ кн) ---- COLLISION FREQUENCY GIYEN BV KANE --- „— » .— . »— « BYTHRANE AND PIGGOTT . ARSORPTION PROFILES DURING PCA H ( km ) шоот Figure 4. Absorption profiles calculated from measured profiles of electron density. Figure 5. Comparison ____ JOMHi ABSORPTION AT RAMFJOKD between calculated absorp- \ tion and measurements wi t h the riometer at Ramfjord. H .00 ало aoo ut — RI0M £TH -------- EISCAT, К Ш COLLISION fK O U lH C Y — - ішг.шш № piseon couitm fkcoucncv ABSORPTION PR0FIIJ5S. The incremental absolution for 30 MHz wa s calcula ted as a function of height from the measured electron density profiles ' using Hultqvist's (1963) formulation of the Sen and V/y.ller (1960) method w i t h collision frequencies given by Kane (1961) and by Thrane and Piggot ( 1 9 6 6 ), These absorption profiles are shown in Figure 4, A comparison b e t w e m the calculated total absorption and that measured b y the 30 MHz riometer at Ramfjord (corrected by a factor of 0.83 to reduce the wide beam r eading to an equivalent zenithal value) is gi v e n in Figure 5. The Kane collision frequency gives the better agreement after 1100 UT. Before that time a relatively large contribution to the absorption came from altitudes below 65 k m where the data are less reliable. A previous compari son in auroral conditions (Ranta et al.,1985) obtained good agreement using the Thrane et Piggot profile, but in that case the absorption was above 75 km; the two collision frequency profiles differ most at the lower altitudes. In fact the shapes of the absorption profiles in Figure 4 do not depend strongly on wh i c h collision frequency profile was used. Table 1 gives the height of m aximum absorption and the wi d t h of the absorption profile between values of half the peak, a c c ording to the Ka n e profile. In night time au r o ral absorption the ma x i m u m occurred between 85 and 90 km, an d the absorption region was 10-15 k m (Ranta et al.,1985). Table 1 HEIGHT AN D W I D T H O F A B S ORPTION REGION UT Height of m a x i m u m (km) Width (km) 1100 66 8 1200 66 8 1 2 3 0 66-69 8 1300 66-69 9 1330 69 8 HO