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.

O.M. Barkhatova et al. In addition, during -01 .00 UT, the values of IMF Bz component change from small negative to positive values. Such situation, according to [Barkhatov et al., 2017; Morley and Freeman , 2007], correspond to the substorm development. Note that the considered time interval corresponds to the night-time magnetosphere sector, within the westward clectrojet (AL) is localized. Its dynamic shows that during this time there really is a bay-like disturbance preceded a non-disturbed period (AL - -20 nT). Fig. 3 shows the dynamics of the Solar wind parameters and the AL index. Black vertical lines indicate the coincidence of foF2 and geomagnetic field H component spectral features at Kazan station. The performed results demonstrate the possibility of synchronous ionospheric and geomagnetic disturbances existence in the class of Pi3 pulsations (periods of 15-30 min) at medium latitudes for local nighttime in the global geomagnetic non-disturbed conditions. The magnetosound nature of observed disturbances is demonstrated by comparing of foF2 critical frequency over the Kazan station and geomagnetic field component spectral patterns over a large spatial region including high, middle and low latitudes. The revealed magnetosound disturbances can be generated by the instability o f westward electrojet. At the same time, these electrojet participates in substorm process as an element of a large-scale three-dimensional current system - a substorm current wedge. During the substorm development, the extended magnetic force lines of geomagnetic tail are subjected to ULF vibration by disturbed magnetized Solar wind. It makes possible to explain such low frequencies of observed disturbances in comparison with resonant MHD oscillations under quiet conditions. Thus, the noted synchronization of ionospheric and magnetic disturbances gives reason for believing that detected disturbances have a magnetosound nature and are associated with substorm activity. Acknow ledgements. This work was supported by grants RFBR №16-05-00608, №16-35-00084 and the Ministry of Education and Science RF State Task № 5.5898.2017/8.9. Acknowledgements for Akchurin A.D. and Yusupov K.M. for provided Kazan ionospheric vertical sounding data. IW component Sotarwind vetottty Figure 3. Interplanetary magnetic field component Bx, By, Bz plots (left panel), Solar wind velocity and concentration (right panel) for September 3, 2014. Vertical black lines indicate the coincidence of foF2 and H component spectral features at Kazan station. References [1] Barkhatova O.M., Barkhatov N.A., Grigoriev G.I. Detection of magneto-gravity waves in the ionosphere by analysis of the maximum observable frequencies on oblique-sounding paths // Radiophysics and Quantum Electronics, V. 52. N 10. P. 683-698. 2009 [2] Barkhatov N.A., Vorob’ev V.G., Revunov S.E., Yagodkina O.I. Effect of solar dynamics parameters on the formation o f substorm activity // Geomagnetism and Aeronomy, V. 57, N.3, P. 251-256, 2017 [3] Morley S.K., Freeman M.P. On the association between northward turnings of the interplanetary magnetic field and substorm onsets // Geophys. Res. Lett. V. 34. L08104. 2007. doi 10.1029/2006GL028891 99