Кустов, А. В. О пороговом электрическом поле для возникновения авроральных неоднородностей с длиной волны около одного метра / А. Кустов, М. Успенский, И. Кангас ; Акад. Наук СССР, Кол. фил. им С. М. Кирова, Поляр. геофиз. ин-т. – Препр. ПГИ-87-06-60. - Апатиты : [б. и.], 1988.

Greenwald et al., 1978) and incoherent scatter (EISCAT, Folkestadt et al., 1983) measurements in a common area is used for analysis below. The E-field ragnitudes were quite low (S-2S mV/m), the electron densities - rather moderate (2- 10® cm"3 ). The latter value* were considerably higher than the instrument sensitivity of the STARE radars, rv 2 • 104 cm'3 by Uspensky et al. (19S3). From the rocket measurements by Pfaff et al. (19e<*) the plasmaphysical electron density threshold for the auroral irregularity excitation is rather low also, <1- 1 0 ^ cm'3 . Thus, the instrumental features of the radars used as well as the plasmaphysical electron density threshold are not important for our consideration 2. EXPERIMENT. The event selected is a part of the special Finnish EISCAT experiment held on November 17, 1983, 2154-2221 UT. The Tromso EISCAT antenna was directed to zenith approximately . The collecting orea for the EISCAT electron density and E-field measurements (the latter is a foot print from the F-region) was about 1 x 1 km at the E-layer level. The STARE auroral backscatter covered a more extensive region of 15 x 50 km over Tromso overlapping the EISCAT beam. The original data integration times for STARE/EISCAT were 20/10 sec respectively. But we have used the 1-minute averaged EISCAT data centered at each STARE 20-sec interval. We have done it to diminish the nonstationarity effects due to the small collecting area of the EISCAT measurements. Details of the experiment were reported by Huuskonen et al.(1966). Experimental data are given in the Fig.l. Electric field magnitude and azimuth are shown in the two upper pannels. The solid lines here correspond to the EISCAT measurements, the STARE data are shown by circles. As a result of the intermittent behaviour of the echoee the STARE data were nonpermanent. The E-field azimuths for the both data sets are in good mutual agreement. However the E-field amplitudes derived from the STARE drift velocity measurements are often 1.5-2 times low than the EISCAT ones. As a whole the EISCAT E- field during the interval under consideration was rather low and varied within 5-25 raV/m. On the middle panel of Fig.l the affective electron densities for the Finnish (F) and Norway <N) STARE radars are shown. They were calculated according to ideas of Uspensky (19851 and Oksman et al. (1986) on the basis of the EISCAT electron density measurements 19