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.

I. V. Despirak et al. Figure 2. Dependence of the onset location of aurora on SYM/H index. The events during the near, late and structured storm recovery phase are marked by yellow, red squares and black triangles, respectively. The dependence of the aurora onset on SYM/H index for substorms during the recovery phase of geomagnetic storms is shown in Fig. 2. It is seen that the events during the near recovery phase (the yellow squares in Fig. 2) occurred mainly near the station zenith or to the South from it. The events during the late recovery phase were observed mainly to the North from Apatity. During the structured recovery phase the auroras originated to South or North from Apatity depending on the SYM/H index values. In generally auroras at higher values of SYM/H are observed to the North from Apatity, and auroras movement from North to South is observed. Substorms at lower SYM/H values originate to the South o f Apatity and the aurora propagation from South to North can be seen. Between these two types o f substorms a “border” zone is formed in which aurora onset can become to the South, over zenith or to the North regarding the station. This zone is in the range form -30 nT to about -55 nT, and it is designated by black vertical lines in Fig. 2. j * Quiet conditions | • Non-stonr.. structures •5 in the soler wind 1 n -f................. - * —* .№ m mm • %m ' i i ! * S ; z i • * * « и • * 3-f -50 -.'(l -10 SYM/И, nT Figure 3. Dependence of the onset location of aurora on SYM/H index. The events during quiet conditions and during non-storm conditions with solar wind structures are marked by blue and red squares, respectively. Fig. 3 shows the dependence of the aurora onset on SYM/H index for events during non-storm conditions. It is seen that no evident dependence of the aurora onset on SYM/H values during non-storm conditions is obtained. Auroras during quiet conditions appeared mostly to the North from zenith or near zenith, and auroras during non­ storm conditions with some solar wind structure occurred at different positions - to the North, near zenith or to the South from Apatity. Discussion In this paper we investigated the location of onset latitude of substorms during storm and non-storm conditions using observations of auroras in Apatity during two winter observational seasons 2014-15 and 2015-16. The most significant result is that the latitude of the substorm onset is controlled by the value of the SYM/H index. This result is in good agreement with the findings of Milan et al. [4]. In particular, one of the main conclusions in this work was that the open flux content of the magnetosphere increased dramatically and substorms became more intense during geomagnetic storm activity, when the SYM/H index was depressed. It has to be mentioned, that in papers [4], [5] the substorm onset latitude was used as a measure of the polar cap size. If the substorm onset latitude decreases, the polar cap is expanded and the open magnetic flux is increased. It turns out that the results found out in the present paper are very similar. 13