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.

“Physics o f Auroral Phenomena ”, Proc. XL Annual Seminar, Apatity, pp. 15-18, 2017 © Polar Geophysical Institute, 2017 Polar Geophysical Institute DAYTIME MAGNETOSPHERE-IONOSPHERE DISTURBANCES IN RESPONSE TO SHARP INCREASES IN THE SOLAR WIND DYNAMIC PRESSURE: EVENT 21-22 JUNE 2015 L.A. Dremukhina1’2, L.I. Gromova1, S.V. Gromov1, V.G. Petrov1 1Pushkov Institute o f Terrestrial Magnetism, Ionosphere and Radio Wave Propagation RAS, Moscow, Russia 2Skobeltsyn Institute o f Nuclear Physics, Moscow State University, Moscow, Russia e-mail: dremukh@izmiran.ru Abstract. In this work we analyze high-latitude ionosphcrc-magnetosphere disturbances, appearing as a response to the sharp fronts o f the solar wind dynamic pressure in the preliminary phase of the storm on 21-23 June 2015, one of the greatest storms in the 24th solar cycle ( Dstmi„ = -204 nT). The analyzed storm is characterized by unusually long initial phase, which was preceded by a long interval (about two days) of extremely quiet solar wind with Bz and By IMF closed to zero. During the storm initial phase, it was observed near the Earth three shock fronts with the dynamic pressure Psw increased to ~ 12, 10 and 60 nPa. The first two fronts were caused by an increase of the solar wind density at low speed, and the most powerful third front was caused also an increase of the solar wind velocity. The storm main phase followed after only the third jump of Psw, when the IMF Bz turned south and reachcd values ~ -37 nT. It is shown that the perturbation scenario in the daytime polar region is determined by the prehistory of conditions in the solar wind, the direction of the IMF and the ratio between values of its component Bz and By. Analysis of spectral characteristics of energetic electrons and ions from the DMSP indicated an increase flux of electrons with energies of 0.1-3 keV and protons with energies of 1.0-10 keV after each dynamic impact of the solar wind. Magnetograms of SWARM satellites, obtained after treatment, showed that field-aligned currents (FAC) with a density o f - 1.5 pA/m2develop in the daytime sector at geomagnetic latitudes ~ (75-85)0after each Psw sharp increase. We believe that the emergence and intensification of these current systems leads to the development of specific polar- latitude negative bay-like magnetic disturbances recorded by ground magnetometers. Introduction The work is a continuation of a comprehensive study of one of the most intensive magnetic storms of the 24th solar activity cycle (SymH — 220 nT), registered on June 22-23, 2015. Earlier [1] the authors considered geomagnetic high-latitude effects at different phases of this storm caused by atypical conditions in near-Earth space. In this work wc analyze daytime high-latitude ionosphere-magnetosphere disturbances in the preliminary phase of the storm, connected to the sharp fronts of the solar wind dynamic pressure (Psw). Most of the earlier works focuses on the effects, associated with sharp fronts o f Psw, at medium and low latitudes. However, it is known that such jumps of Psw can cause both rapid reorganization o f the convection system [2] and the appearance of a new systems of field-aligned currents (FAC) in the daytime sector of high-latitude ionoshpere [3]. For our study we used 1-min data on solar wind parameters and simultaneous ground measurements of Scandinavian profile IMAGE and antipodal on LT North-American network of observatories, as well as data on energetic ions and protons fluxes from DMSP satellites over the auroral oval, and measurements of the magnetosphere magnetic field by low-orbit satellites of the SWARM mission, the trajectory of which lies near midday- midnight meridian. The solar wind parameters and ground-based observations Fig. 1 shows 1-min variations of the By, Bz components of IMF, the density Np and the velocity Кof the solar wind, and the geomagnetic activity index SymH for June 21 - 22,2015 ( http://omniweb.gsfc.nasa.gov ) . It can be seen in Fig. 1 that during the initial phase o f the storm, three sharp Psw jumps were recorded, mainly due to sharp increases in Figure 1. 1-min variations in the solar wind and IMF parameters and the SymH index for June 21- 22, 2015. 15