Physics of auroral phenomena : proceedings of the 37th Annual seminar, Apatity, 25 - 28 February, 2014 / [ed. board: A. G. Yahnin, N. V. Semenova]. - Апатиты : Изд-во Кольского научного центра РАН, 2014. - 125 с. : ил., табл.

V. Guineva et at. Discussion We studied three cases of substorm generation and development under different conditions. In the first case, the geomagnetic conditions were highly disturbed. A magnetic cloud passing by the Earth caused a strong geomagnetic storm (DS1—140 nT). The auroral oval was located at lower latitudes, to the South of Apatity. Both examined substorms occurred consecutively during the main phase of the storm. Their onset locations were as well to the South of Apatity. Thus, the polar edge of the auroral bulge was observed to move fast towards North, to reach and surpass the zenith. After the second intensification, the substorm bulge spread over the whole field of view, the station staying inside the bulge. In the second case, the geomagnetic conditions were also disturbed. There was a recurrent stream in the solar wind. A geomagnetic storm was generated (Dst=-65 nT). Three substorms were examined. Two of them developed during the main phase of the storm. The substorm onset was to the South of Apatity and during the auroral bulge evolution the polar edge of the bulge moved in S-N direction over the station. The third substorm developed during the recovery phase the storm. The auroral activity was to the North from the station and the movement of die equatorial edge of the substorm bulge could be seen in N-S direction before the spread of the bulge all over the field of view. Case 3 represents a substorm generated in quiet conditions. In this case the auroral oval was at higher latitudes, to the North of Apatity. The substorm onset was to the North of the Apatity. These observations confirm typical morphology: in disturbed geomagnetic conditions, when storms are generated, the auroral oval lies at lower latitudes. Thus the substorm onset is located to the South of Apatity and the motion of the polar edge of the substorm bulge can be seen moving in S-N direction over the station. This situation was observed mainly for |Dst|>40nT. And vice versa, under quiet conditions or during the recovery phase of a geomagnetic storm, the auroral oval is located at higher latitudes, to the North of Apatity. The substorm arises to the North and during the bulge expansion the movement of it equatorial edge in N-S direction can be observed. This situation was observed mainly by |Dst|<40nT. Conclusions It is shown that 2 types of substorm development occur over Apatity. First type: substorm onset is to the South of Apatity, and the “usual” development of the substorm bulge is seen - from South to North; the polar edge of the bulge is observed to pass over zenith. Second type: the auroral oval is situated at higher latitudes, substorm generates to the North from Apatity, and the movement of the auroral bulge to the South is seen from Apatity, i.e. the equatorial edge of the auroral bulge is observed. It is shown that the first type o f substorm development over Apatity happens during geomagnetic storms (|Dst|>40nT), associated with both magnetic clouds and high speed recurrent streams of the solar wind. The second type of substorm development is observed during quiet (non-storm) conditions or during the storm recovery phase (|Dst|<40nT). It should be noted that such research is important for understanding of the regional space weather problems. Acknowledgements. WIND data used in this study were taken from OMNI through http://cdaweb.gsfc.nasa.gov/cdaweb/istpj mblic/. We are grateful to J. N. King and N. Papatashvili, the heads of the experiments conducted with these instruments. The paper was partly supported by the RFBR Grants 12-05-01030 and Program No 22 of the Presidium of the Russian Academy of Sciences (RAS). The study is also a part of a joint Russian - Bulgarian Project 2-14 of PGI RAS and IKIT-BAS under the Fundamental Space Research Program between RAS and BAS. 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