Координированные наблюдения авроральных явлений 1-2 декабря и 11-12 декабря 1977 г. на Кольском полуострове и в Финляндии / С. А. Черноус, Н. И. Федорова, Г. А. Логинов и др. ; Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т. – Препр. ПГИ-79-3. - Апатиты : [б. и.], 1979.

Th.ua it is clear that essential softening in the optical range ( 100 eV - 10 keV) of electron precipitation energy spectra occurred in the morning sector. It is interesting to compare the behaviour of auroral particles ( E £ 1 0 keV as derived from spectral ratios) with the behaviour of high energy particles ( Ей;40 keV) which becomes apparent through riometer absorption. The source re gions and the precipitating mechanisms of these two types of particles must be very different. Fig.8 shows the intensity ratio I 6300/1 5577 in loga rithmic scale on Dec. 1/2. After 02.30 UT this relationship starts to grow and after 3*40 UT it exceeds 3 which indicates increased soft component in the particle precipitation spec tra.High energy part >40 keV of spectra is also decreasing after 02.00 UT as can be seen in the multifrequency analysis data shown below the intensity ratio curve Гб] . In prin ciple when is small ( close to 1) precipitation is intensive in the high energy range and when n is large (close to 2) precipitation is softer. A third energy parameter А/ \/f, where A is auroral absorp tion and I auroral intensity, also can be used to study the variations in auroral precipitation spectra (Fig.8). According to Holt f ? ] and Berkey [8] there is a linear 8. dependence between the squre root of auroral intensity and riometer absorption when special conditions are fulfilled. This is because I is propotional to the ionization rate and A is propotional to concentration of electrons. However if this dependence is broken the changes in energy spectrum are mainly responsible for it. According to experimental data [9] the higher the magnitude of the parameter А/ >TT is, the harder the spectrum of precipitating particles. Fig.8 shows that in the morning sector of Dec. 1/2 1977 at 02 - 05 UT the oscillations of energy spectrum are revealed in this parameter and after 04.00 UT particle precipitation softened. Thus the various data presented in Section 2 and the ana lysis made above confirm that in addition to substantial so ftening of energy spectrum and precipitating soft electron