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.

are observed rising from the polar cap background level. These spikes are assumed to be associated with sun-aligned polar cap auroras. A photometer operated on a routine basis at Godhavn, Greenland (76.5° corr.geom.lat.) scanned the magnetic meridian from north to south in 6300 A once every four О minutes. The duration of. the scan was 30 s. The 6300 A emission may be a signature of precipitation of low-energy electrons (Shepherd,1979). It has been demonstrated (Lassen et al.,1986) that the spatial distribution of dif- О fuse 6300 A emission during quiet conditions is identical with the quiet time electron precipitation pattern defined by the observations from the DMSP- satellite. Therefore, the photometer observations may be used to supplement the DMSP precipitation measurements in the determination of the boundary position; This reduces the time resolution in the observations (at a fixed meridian) to 4 minutes. Visual auroras were monitored by all-sky camera network in Greenland using 20 s exposures every two minutes. The camera stations in South Greenland, which cover the region between 65° and 73° corr.geom.lat., hud clear sky all night.The region from 68° to 75° is covered by Kapisillit from 0330 UT, while the northernmost region, above 83°, is covered by Thule from 02 UT. The Godhavn camera had technical failures, and the remaining stations had poor weather conditions. Thus we have been able to record the aurora with all-sky cameras in the latitude range b5°-75° and north of 83° corr.geom.lat., while the latitude range 70°-83° was monitored by the meridian scanning photo meter at Godhavn. RESULTS. The quiet precipitation pattern. Lassen et al.(1986) studied the statistical boundaries of the doiible-belt obtained during northern hemisphere orbits with Kp=0 or 1 and demonstrated that whereas the quiet Feldstein auroral oval is included in the outer higher-energy belt, the high latitude daytime auroras are embedded in the inner lower-energy belt. The polar dist ance of this belt was found to decrease rapidly at ab.03 MLT in accordance with the fact that during magnetic calm discrete aurox-al forms tend to light up sporadically at high latitudes at this hour (Lassen,1961,1963,1969,1972). A corresponding increase of polar distance was demonstrated to occur at ab. 21 MLT. Fig. 4. Distribution of elect ron precipitation boundaries in a geomagnetic latitude/time graph. Full curves show northern hemisphere statistic boundaris for K p =0 from a data set obtained during six north ern winter months of 1978 to 1980. Boundaries observed on N o v . 29,1 984 during the interval 00 to 0510 UT during northern and southern passes are indicated by dots. Also shown is the satellite orbit at 0240-0301 UT, data from which are presented in Fig, 3 , I08