Physics of auroral phenomena : proceedings of the 39th annual seminar, Apatity, 29 February-4 March, 2016 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2016. - 167 с. : ил., табл.

S.M. Cherniakov et al. takes place at the heights of 73-81 km. Here the electron concentration has decreased more than ten times. The third profile (10:34 UT) is drawn in fifteen minutes after the eclipse maximum. PEC shows increase in the electron concentration at the heights over 73 km, and at the heights of 68-72 km shows reduction. At the same time at the height of 85 km the local maximum of the layer is formed. The fourth PEC (11:11 UT) is drawn ten minutes until the end of the eclipse. Lower than 80 km the profile of the electron concentration is similar with the PEC before the eclipse, i.e. it has returned to the initial state. Higher than 80 km the electron concentration has increased and at the height of 83 km the local maximum was created. The fifth PEC (12:05 UT) is drawn for the ionosphere after the eclipse. It is visible that it has returned to the condition of the ionosphere before the eclipse. The behavior of PEC in genera! corresponds to approach of "short night", i.e. reduction of the ionizing radiation during the eclipse. Electron concentration profiles, 19 March 2015 Electron concentration profiles, 20 March 2015 8 5 SO Ъ 75;- 7 0 6 5 10 ' - 0 9 :1 5 U T — 1 0 :0 7 U T S - - 1 0 :2 1 U T *v "X? - 1 1 :1 5 U T _j -*-12:06 U T 4 / fty A f 7 ' 4 * у 1 j J a 1 ' — 1 8 5 „ so §75 7 0 10 10* 10 Electron concentration, cm * 10 6 5 - 0 9 : 1 5 U T ............................................ - 1 0 : 0 4 U T — 1 0 :3 4 U T - 1 1 :1 1 U T ____\ J - 1 2 : 0 5 U T Чг— — Г > \ ( Я A. * M - F T "C •" v i 4 * T 7 b ...ж-' •a6 V c r ( V 4 ^ ? к . Y > ........................... 6 10 10 10* 10 Electron concentration, cm '1 Figure 3. The electron concentration profiles in the control day on March 19, 2015 (at the left) and during the eclipse on March 20, 2015 (on the right) 10 In Fig. 4 the behavior of the electron concentration at the heights of 68 km and 90 km is shown. Letters В, M and E are designated the beginning, the maximum and the end of the eclipse, respectively (these designations are identical ones in all subsequent figures). A geometrical eclipse function represents the ratio of an open part of the solar disk unscreened by the Moon disk to the full disk of the Sun. It changes from one (1.0) before an eclipse and to zero (0) at a total eclipse. As an ionization function during an eclipse depends on an open part of the solar disk, one may say, that the behavior of an ionization function during an eclipse is similar to behavior of an eclipse function. Since an eclipse function is normalized value, it can be adjusted to a profile of the electron concentration at the chosen height and we can compare their behavior. The shaped line has shown behavior of the reduced eclipse function. Actually this is the comparison of behavior of an ionization function and a profile of the electron concentration at the chosen height. By consideration of behavior of the electron concentration at different heights it has turned out that during the eclipse the good consent of behavior of a temporal profile of the electron concentration with the reduced eclipse function was observed only at some heights. In Fig. 4 changes of the temporal profile of the electron concentration at the height of 68 km during the eclipse well corresponds to changes of the profile of the reduced eclipse function (i. e. an ionization function). During the eclipse typical temporal profiles of the electron concentration were profiles for which it was impossible to define a minimum of the electron concentration at the eclipse maximum. The example of it is the profile of the electron concentration at the height of 90 km (Fig. 4). The similar behavior of profiles of the electron concentration is caused, probably, by wave processes at various heights of the lower ionosphere. The typical periods of Brunt-Vaisala frequencies in the atmosphere are equal 5-10 minutes depending on a condition of the atmosphere [Brunelli, Namgaladze, 1988]. Therefore in the electron concentration and amplitudes of ordinary and extraordinary waves presence of wave processes with the periods from 10 to 80 minutes (internal gravity waves) has been analyzed. For the analysis of the obtained data the digital bandpass elliptic filter which parameters have been described above was used. Figure 4. Temporal profiles of the electron concentration at the heights of 68 km and 90 km during the solar eclipse on March 20, 2015 94