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.

1. INTRODUCTION. It is a generally accepted opinion that the 140/398-MHz radar aurora backscatter {irregularity wavelengths are 1- 0.4 m respectively) is observed only «hen the ionospheric electric field exceeds some threshold values of 20-30 mV/m (Tsunoda and Presnell, 1976; Cahill et al., 197S; Moorcroft, 1979). It seens quite reasonable that this effect is a result of the Farley-Buneman (FB) instability sudden onset. However, for the 50-MHz radar backscatter ( A = 3 m) the E-field threshold can be smaller to about 10 aV/m (Siren et al., 1977). It makes it difficult to apply the FB mechanism to the explanation. The irregularity excitation for such low E-field values is probably due to the influence of the gradient-drift (GD) instability (Siren et al., 1977; Fejer and Kelley, I960). The radar auroral backscatter can be observed also if in the scatter volume there exist some domains where the ionospheric parameters are different. One can cell it an unresolved microstructure. Then the auroral backscatter can be detected if in the patches of the volume the local E-fields are more than the E-field threshold for the FB instability excitation (Siren et al., 1977). However subsequent experiments (Greenwald, 1979; Nielsen et al., 1982; Andre, 19B3) have shown even the 'tl-m irregularities can be observed for the irregularity drift velocities equal or less than 100- 200 m/s. If we suggest the irregularity drift velocity to be close to the ExB electron drift, the F-fields for the mentioned events are around 5-10 mV/m (Greenwald, 1979; Greenwald et al., 1978; Nielsen and Schlegel, 1985). The 1-m irregularity appearence, in a case of the irregularity drift velocities being extremely low,can be attributed to a strong ionospheric neutral wind. The neutral wind could support the GD and FB turbulence development. At the same time the low drift- velocity irregularities can be created also by the neutral gas turbulence (Nielsen et al., 1982). As a consequence of.a number of the irregularity sourses an application of the coherent scatter drift velocity data to derive the ionospheric E-fields and the irregularity E-field threshold can be matched with errors and uncertainities. One of the ways to resolve these difficulties is to use the E-field data in the backscatter area obtained by other means e.g. by the incoherent scatter radar measurements The present paper is involved in the question on the E-field threshold for the 1-m irregularity appearence in the auroral electrojet. The short period of joint coherent scatter (STARE, 18