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.

LATITUDE PROFILES OFWNHz ABSOmiOHjm FEB 16 «OOUT / / -- 1200 1700 MO —I-----r —I- 65 4- «H0UT 1000 0 950 2- 0940 0950 n 67 £1 «10UT 1000 09S0 0940 09)0 Figure 2. Latitude pr o files of absorption at selected times during the PCA. Top - chain 1 j bottom - chain 2 j left - event growth* right - event decay. Chain 2 is approximately magneti cally north-south through Ramfjord. chain 1 is a north-south chain some 320 k m to the east. INVARIANT LATITUDE (*) subjected to further smoothing in both time and altitude. Electron density as a function of altitude wa s determined from the scattered power assuming thermal equilibrium between ions and electrons. To reduce error in low altitude data due to receiver recovery effects the rece ived power wa s approximated by the 104JJS lag of the calculated autocorrela tion function of the signal. This approximation is valid for low signal to noise ratio and sufficiently long correlation tine and was used for altitudes below 80 km. The received signal was extremely w e a k and in order to increase the statistical accuracy of the data a method due to M.Lehtinen and A.Huusko- n e n (1986) was used to combine data from power profile channels and pulse code channels. This method was applicable at altitudes above 80 km. Figure 3 shows the electron density profiles obtained for 6 times during the event. Points are given every 3 km, each being a n average over 3 km in height and over 10 minute of time. The tail of ionization below 90 km, attri buted to proton ionization, shows no sharp gradients above 70 km. The change i n the profile during the event clearly suggest a gradual softening of the p roton spectrum. Values of electron density range between 1200 cm (at 65 km) and 15000 om”^ (at 90 km). The peak value occurs earlier in the event at the lower altitudes, consistent wi t h a softening of the proton spectrum as the event proceeded. H,m 60 70 60 \ j 1 SI 5 у f W . т ш , порЦТ. Ю.0Щ. m u r . то щ . 0 / mo/ о/ 5000/ tom о/ 5000/ WOOO 0 / 5000/ moo 01 5000/ moo 5000 / moo 5000/ wooo Figure 3.Electron density profiles de termined at EISCAT. E a c h point is a n aver age over 10 minutes and over 3 k m of alti tude. Each profile is displaced 5000 units along the horizontal scale for clarity. ELECTRON BENSITY few'5) I09