Physics of auroral phenomena : proceedings of the 38th annual seminar, Apatity, 2-6 march, 2015 / [ed. board: A. G. Yahnin, N. V. Semenova]. - Апатиты : Издательство Кольского научного центра РАН, 2015. - 189 с. : ил., табл.

“P hysics o f Auroral P henom ena", Proc. XXXVIII A nnu al Sem inar, Apatity, pp . 7-10, 2 0 1 5 © Kola Science Centre, Russian Academy o f Science, 2015 Polar Geophysical Institute SUBSTORMS OBSERVATIONS DURING GEOMAGNETIC ACTIVE PERIOD AT THE BEGINNING OF MARCH 2012 V. Guineva1,1.V. Despirak2, B.V. Kozelov2 'Space Research and Technology Institute (SRTI), Stara Zagora Department, BAS, P.O. Box 73, 6000 Stara Zagora, Bulgaria, e-mail: v_guineva@yahoo.com 2Polar Geophysical Institute, Apatity, Russia Abstract. The period 7-17 March 2012 is one of the most geomagnetically active periods during the ascending phase of Solar Cycle 24. Magnetic storms occurred on 7, 9, 12, and 15 March, these are called the SI, S2, S3, and S4 events. These storms were caused by Sheath, MC and HSS, the detailed scenario for all four storms were different. Measurements of the Multiscale Aurora Imaging Network (MAIN) in Apatity and data of IMAGE magnetometers network have been used to verify the substorms onset and subsequent development. Substorms during the chain of 4 geomagnetic storms in the interval 7-17.03.2012 were studied and the characteristics of these substorms were compared to different interplanetary conditions. It was shown that substorms, originated during strong geomagnetic storms provoked by interplanetary shocks and magnetic clouds, near the Dst minimum, occurred to the South of Apatity, and substorm auroras expanded in North direction. For substorms during the late recovery phase, auroras were observed to the North of the Apatity station, and their motion from North to South was registered. Introduction Events of strong geomagnetic activity are of special interest because magnetic storms can affect the energetic systems, the space crafts or the ground based systems. That’s why coordinated actions of the scientific community are needed to perform and gather observations, to create models of the whole chain o f phenomena from the Sun to the Earth in order to make successful predictions of space weather and to prevent failures in the technologic infrastructure by reason of strong geomagnetic storms [1]. It is known that the following types of solar wind mainly generate the geomagnetic storms: interplanetaiy CORONAL MASS EJECTIONS (ICME) including Sheath- region and body of ICME (magnetic cloud, MC) and Corotating Interaction Regions (CIR) (e.g. [2], [3]). CIR is a region of the interaction of a high-speed recurrent stream with the undisturbed solar wind. CIR is determined as a region with magnetic field and plasma compression [4]. During a solar maximum, most common are the sporadic flows associated with coronal mass ejections (CME) [5]. Near the Earth they are observed as magnetic clouds (MC) (e.g. [6]). MC are characterized as regions, where the magnetic field strength is higher than the average, the density is relatively low, and the magnetic pressure strongly exceeds the ion thermal pressure, the magnetic field direction changes through the cloud by rotating parallel to a plane which is highly inclined with respect to the ecliptic [6]. Ahead of MC, a region of interaction with undisturbed solar wind (Sheath) is known to form, which is characterized by high density, increased pressure and strong IMF variability. It should be noted that there are differences between storms generated by Sheath, MC and CIR (in intensity, recovery phase duration, etc.) (e.g., [7], [8]; [9]). However there are more complicated storm cases, when the magnetic storms are caused by several sources in the solar wind, coming consecutively one after the other or partly overlapping. Such an example is the event of strong geomagnetic activity 7-17 March 2012, which is one of the most disturbed periods during the ascending phase of Solar Cycle 24. This active interval was examined and the detected features were described ([10], [11], [12]). During this period four consecutive magnetic storms occurred on 7, 9,12, and 15 March. The peak intensities are ~ - 98 nT, - 148 nT, -67nT, -79nT, respectively. These storms were caused by Sheath, MC and HSS, and the detailed scenarios for the storms were different. Each individual storm was discussed in some detail in previous papers [10], [11]. In our work three storm events during the strong geomagnetic activity period 7-17 March 2012 were considered. We have measurements from the Multiscale Aurora Imaging Network (MAIN) in Apatity during the first, the second and the third storms of this period. Below two events of substorms observations during the first and the second storms of this geomagnetic activity period are presented. Data Measurements from the Multiscale Aurora Imaging Network (MAIN) in Apatity during the strongly disturbed period in March 2012 have been used. The all-sky cameras observational system has being built in Apatity since 2008. The cameras characteristics, their mutual situation and the measurement process are described in detail in [12]. Solar wind and interplanetary magnetic field parameters were taken from OMNI database (http://sdaweb.gsfc. nasa.gov/cdaweb/istp_publicl). 7