Physics of auroral phenomena : proceedings of the 36th Annual seminar, Apatity, 26 February – 01 March, 2013 / [ed. board: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2013. - 215 с. : ил., табл.

*Physics o f Auroral Phenomena”, Proc. XXXVI Annual Seminar, Apatity, pp. 9-12, 2013 © Kola Science Centre, Russian Academy of Science, 2013 Polar Geophysical Institute MAGNETIC RECONNECTION SITE IN THE MAGNETOTAIL DURING DIFFERENT SOLAR WIND STREAMS I.V. D espirak1, A .A . L ubchich1, R. Koleva2 streams have different nature during different phases of solar activity. During the declining phase and minima o f the solar cycle predominate the recurrent streams (RS) originating from coronal magnetic holes. During solar cycle locations o f the tail magnetic reconnection site during substorms connected with solar wind magnetic clouds (MC) show that magnetic reconnection in the magnetotail takes place closer to Earth when substorm is observed during MC, and further in radial distance for substorms during solar wind recurrent streams. Introduction Recently the authors in Nagai et al. (2005) showed that the location of the reconnection site in the magnetotail depends on the phase o f the solar activity cycle. They found out that during solar cycle maximum magnetic reconnection is observed nearer to Earth than during the minimum o f solar activity. It is well known that solar wind is not a uniform flow; various large-scale structures and streams exist within it (e.g. Pudovkin, 1996; Yermolaev et al., 2009). Besides during different solar activity phases prevail different solar wind flows ( Krieger et al., 1973', Burlaga et al., 1982; Richardson et al., 2001). During the declining phase and at the minimum of solar activity high speed recurrent solar wind streams (RS) originating in coronal holes prevail while in solar activity maximum prevail flows from coronal mass ejecta which are observed as magnetic clouds (MC) near Earth. In this work we will investigate the reconnection site location in the magnetotail during substorms observed under different solar wind structures. When a reconnection site passes along a satellite in the night plasma sheet first a fast earthward plasma flow is registered and then - a fast tailward flow. In one of the main substorm models - NENL, the observation of a fast flow reversal is interpreted as a tailward motion of the reconnection site past the satellite {Hones, 1979; Angelopoulos et al., 1996; Petrukovich et al.’, 1998; Yahnin et a l, 2006). In another substorm model, the Current Disruption model, the observation of a fast floe reversal is interpreted as a passage along the satellite the current disruption region (e.g., Lui et a l, 2008). The goal of this work is to determine the reconnection site location in the magnetotail associated with substorms developed under different solar wind streams - recurrent streams (RS), magnetic clouds (MC), and the region of compressed plasma in front of these streams (Sheaths and CIRs). For this purpose we used Geotail position at the moment of observation o f an X-line moving tailward (observation of a fast flow reversal) for cases related with different solar wind streams. The auroral disturbances are studied by Polar UVI data in the LBHL band (1600-1800A); plasma parameters are taken from Geotail LEP measurements, and magnetic field from MGF measurements; the solar wind and interplanetary magnetic field parameters measured by Wind spacecraft were downloaded from OMNI database. The events were selected using the following criteria: 1) The auroral disturbances should be observed by the UVI onboard Polar; 2) The auroral disturbances should be observed during Sheath, CIR, MC or RS solar wind structures; 3) The meridian of the Geotail footprint should cross the auroral bulge; 4) Geotail should be in the night plasma sheet. The criterion /? > 0.1 (/? is the ratio o f kinetic plasma pressure to magnetic pressure) and eye inspection of ion and electron spectra are applied for the plasma sheet identification. 1 Polar Geophysical Institute, RAS, Apatity, M urmansk region, 184200, Russia, e-mail: despirak@gmail. com 2Space Research & Technologies Institute, BAS, Sofia, Bulgaria Abstract. In this work we discuss the problem of the magnetic reconnection site location in the magnetotail during substorms associated with different solar wind streams. It was shown recently that solar cycle variations o f the solar wind control the location of magnetic reconnection in the tail. A well-known fact is that solar wind high-speed maxima the flare streams connected with coronal mass ejections prevail. We analyze the relationship between the and recurrent streams. We use data from Geotail spacecraft in the magnetotail and solar wind parameters from Wind spacecraft observations; the auroral bulge parameters were obtained by the Ultra Violet Imager onboard Polar. We Data used 9