Physics of auroral phenomena : proceedings of the 39th annual seminar, Apatity, 29 February-4 March, 2016 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2016. - 167 с. : ил., табл.

“P hysics o f Auroral Phenomena", Proc. XXXIX Annual Sem inar, A patity, pp. 11-14, 2 0 1 6 © Polar Geophysical Institute, 2016 Polar Geophysical Institute SUBSTORM OBSERVATIONS OF THE MAIN IN APATITY DURING St. PATRICK S DAY GEOMAGNETIC STORMS IN 2013 AND 2015 I.V. D esp irak 1, B.V. Kozelov1, V. Guineva2 1 Polar Geophysical Institute, Apatity, Russia 2Space Research a n d Technology Institute (SRTI), Stara Zagora Department, BAS, P.O. Box 73, 6000 Stara Zagora, Bulgaria e-mails: despirak@ gmail.com , boris.kozelov@ gmail.com , v_guineva@ yahoo.com Abstract. This study presents an analysis of the ground-based observations of the auroral disturbances during two St. Patrick's Day geomagnetic storms on March 17, 2013 and 2015. The first event on 17 March 2015 is the so- called “St. Patrick’s Day 2015 Event”. This is the principal event covering the interval from 15 to 18 March 2015, in which solar eruptive phenomena (a long-enduring C9-class solar flare and associated CME(s) on 15 March) and a strong geomagnetic storm on 16-18 March (Max. Dsl was -228 nT) were reported. This magnetic storm is the largest one observed in the current solar cycle. The second event is the period on 17-18 March 2013 when a strong geomagnetic storm (the DS1index ~ -140 nT) was developed. This storm was caused by magnetic cloud (15 UT, 17 March - 6 UT, 18 March 2013) in the solar wind. Object o f our study were the substorms observed during these periods. Observations of the Multiscale Aurora Imaging Network (MAIN) in Apatity have been used. Solar wind and interplanetary magnetic field parameters were taken from OMNI data base. Substorm onset time and the subsequent development were verified by data of IMAGE magnetometers network and by data of the all-sky camera at Apatity. The particularities in the behaviours of substorms connected with different storms during these two interesting strongly disturbed periods are discussed. Introduction It is known that geomagnetic storms may be caused by the following types of solar wind: ICME including Sheath region and body of ICME (magnetic cloud, MC) and CIR- region (e.g. [1]). It should be noted that there are differences between storms generated by Sheath, MC and CIR (in intensity, recovery phase duration, etc.) (e.g., [2], [3], [4]). However, there are also 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 case, for example, is one event of strong geomagnetic activity on 7-17 March 2012 which was examined recently (e.g. [5]). In our work we considered two strong storm cases during March 2013 and March 2015. The geomagnetic storm occurred on 17-19 March 2015 was the record in strength over the past ten years. It was the strongest storm in the 24th solar cycle. It was called “St. Patrick’s Day 2015 Event” . The second event is the period 17-18 March 2013 when a strong geomagnetic storm was developed. On 17.03.2013 a magnetic cloud passed by the Earth, and a geomagnetic storm with DS t ~ -140 nT developed. We considered substorms observations during these two disturbed periods, in March 2013 and March 2015, in Apatity. We have measurements from the Multiscale Aurora Imaging Network (MAIN) in Apatity during these two St. Patrick's Day geomagnetic storms. Below two examples of substorms observations during the first and the second storms are presented. Data Measurements from the Multiscale Aurora Imaging Network (MAIN) in Apatity during the strongly disturbed periods in March 2013 and in March 2015 have been used. Substorm presence was verified by ground-based data of IMAGE magnetometers network (using the meridional chain NUR-NAL). Solar wind and interplanetary magnetic field parameters were taken from the 1-min sampled OMNI data base (spacecraft-interspersed, near Earth data) of the Coordinated Data Analysis Website ( http://cdaweb.gsfc.nasa.gov/cgi-bin/eval2.cgi ) . To study the substorm development data from the Apatity all-sky camera (images and keograms) and the Guppy F-044C (GC) camera with a field of view -67° (keograms) were used. Observations Case 1: 17 March 2015 The time interval 17 - 20 March 2015 is one of the strong geomagnetic storm of the periods of the ascending phase of SC24. An overview of the interplanetary conditions during this examined period is presented in Fig. 1. Fig. 1 shows the solar wind conditions taken from the OMNI database for the period 16- 27 March, 2015. A severe geomagnetic storm (G4) developed during this time. It was the result of a pair of CME’s which left the Sun on 15 March 2015, may be unexpectedly combined spreading towards Earth and formed a large shock front crossing 11