Движение на восток радиоавроры и петель свечения в утреннем секторе : [науч. докл. ПГИ-79-1] / Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т ; М. В. Успенский, А. В. Кустов, Е. В. Пудовкина и др. – Препр. ПГИ-79-1. - Апатиты : [б. и.], 1979.

ting increment joining the two-stream and the drift-gradient modes of the instability, wa.s discussed by Farley and Fejeir, 1975. But it is noed usually that for the characteristic sca le of the irregularities accross the magnetic field is less than 3 m (the radar frequency 50 MHz) the role of the drift- gradient mode in the summary instability increment is negli gible (see, for example Greenwald's review,1979). As our ob servations were carried on at 93 MHz this conclusion demands a special remark. Really this conclusion is doubtless for the evening diffuse radioaurora. Remember that the background gradient (for example, the component of the vertical gradi ent of the electron density that is perpendicular to the mag— netic field) is usually estimated by the value L~5X10 m. But here we discuss the horizontal gradients in the wake of the moving arc. It is evident that such gradient is higher (the value 1 will decrease because Ь - is the characteristic of electron density scale length). Indeed after the passage of the arc the density is decreasing a ording to n(t)=n0/(1+«tnQ), where n-the initial electron density in the arc, nQ-the mean electron density, iX-the recombination coefficient. Suggest the number of ion pairs produced in a unit volume per unit time inside arc is q, but outside is zero. Then the changing of the density from 2n to n will take place during the time t=1/2cm. Then the gradient of the electron density is nume rically equal to the length that was passed by the arc with the velocity during the time t, i.e. L=V^/2an. Here L is -*-0 by V -*•0 or n^-»00. The meridional velocity of the arcs is equal to 300 m/sec for the discussed loop. Suggest that the height of the lower border of such aurora is 100 km and —7 3 —1 the recombination coefficient is(X=4x10 sm sec . Then 5 times (L=10^m) gradient increasing near the usual diffu3e radioauroral event for example would be observed for the 5 —3* electron density 3.8*10 sm J, and it is admissible for the excitement. Thus the drift gradient member in the instabi lity increment formula can be approximately 5—10 times hig her in the wake of moving arc than in the typical situation of the usual radioaurora. Kear the northern arc the insta— 28