Physics of auroral phenomena : proceedings of the 40th annual seminar, Apatity, 13-17 March, 2017 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2017. - 143 с. : ил., табл.

Effect o fthe IMF By on dayside polar geomagnetic disturbances Observations The space weather conditions during these two events are presented in Fig. 1. The dayside bays on June 23,2015 and May 24,2000 developed during long-duration untypical for recovery phase intervals of the strong negative (-15 nT) IMF Bz under non-variable solar wind velocity (-600-700 km/s) and low dynamic pressure. The IMF By was weakly positive during whole examined interval o f June 23,2015 (Fig. 1, left), but on May 24, 2000, the IMF By sharply changed from positive to strong negative (-18 nT), remained negative during two hours and then returned to positive again (Fig. 1, right). In the both examined events, the high latitude geomagnetic disturbances in the nightside sector o f the auroral zone was similar, AL -index changed weakly near -1000 nT. Fig. 2 demonstrates the IMF Bz and By components and IMAGE difference magnetograms o f X component o f the geomagnetic field for June 23, 2015 (left), and May, 23, 2000 (right). They represent the geomagnetic variations compared to the most magneto-quiet 2009 level [Levitin et al., 2014]. The considered dayside magnetic bays marked by yellow. The auroral oval position according to the OVATION model for the first event and the electron image from the IMAGE satellite for the second one are shown in Fig. 2 as well. June 23, 2015 May 24, 2000 "И Bz nT “ ^ 15 О -16E- L b >- oo «Г iV ~ I t Figure 2. a) IMF Bz and By components and IMAGE difference magnetograms for June 23, 2015 (left) and May 24, 2000 {right). Examined dayside magnetic bays are marked by yellow; b) Left the auroral oval position according to the OVATION model. Right: the electron image from the IMAGE satellite. Yellow/black circle marks the location of the high latitude IMAGE stations. On June 23, 2015 (Fig. 2, leftt), the long-duration dayside negative magnetic bay (-350 nT) was recorded at the high-latitude IMAGE stations (NAL - SOR) while the IMF Bz was more intensive than the IMF By. The ratio o f the \Bz\!\By | я 3. On May 24, 2000 (Fig. 2, right), the sequence of positive and negative bays occurred in the dayside sector of the polar latitudes (Ф > 70°) under the positive or negative IMF By respectively. The ratio of the \Bz\/\By \ varied from 0.3 to 0.9. 20