Physics of auroral phenomena : proceedings of the 33rd Annual seminar, Apatity, 02 - 05 March, 2010 / [ed.: A.G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 206 с. : ил.

“Physics ofAuroral Phenom enaP roc. XXXIIIAnnual Seminar, Apatity, pp. 2 5 - 28, 2011 ©Kola Science Centre, Russian Academy of Science, 2011 Polar Geophysical Institute BEHAVIOR OF THE 5577Л AND 6300A EMISSIONS DURING SUBSTORMS CONNECTED WITH RECURRENT SOLAR WIND STREAMS V .H . Guineva1,1.V . Despirak2, R .W em er1, E. T rondsen3 1. Space and Solar-Terrestrial Research Institute, BAS, Stara Zagora, Bulgaria, e-mail: v suinevaSivahoo. com: 2. Polar Geophysical Institute, RAS, Apatity, Murmansk region, 184209, Russia; 3. University o f Oslo, Department o f Physics, Oslo, Norway; Abstract. The behaviour o f the auroral emissions 5511k and 6300A and the ratio I 6300 /I 5577 during substorms occurred at the time of recurrent streams (RS) has been examined. The development of the substorm bulge is followed up. The variations of the emissions depending on the different locations o f the substorm bulge with respect to the point of observation have been studied. Estimations of the particle precipitation spectra at the polar edge of the auroral bulge and inside it have been obtained. For the study, data from the All-Sky Imagers at And 0 ya Rocket Range (ARR), Andenes, Norway (69.3°N, 16.03°E) and at the Auroral Observatory, Longyearbyen, Svalbard (78.20°N, 15.83°E) from the observational season 2005-2006 have been used. Additional data concerning the solar wind parameters, IMF, the precipitating particles and the magnetic field are used from the WIND satellite and the IMAGE magnetometer network to determine the recurrent streams and the substorms during RS. Introduction It is known that the spectral characteristics of the aurora depend on the type of the solar wind flows (e.g. Hviuzova and Leontyev, 1997, 2001). The solar wind flows are different according to the state o f the solar activity. During a solar minimum, the recurrent streams (RS) originating from coronal magnetic holes, characterized by a 27-day recurrence, are predominant (Pudovkin, 1996). During a solar maximum, most common are the sporadic flows associated with coronal mass ejections (CME) (Wang and Sheeley, 1994). Near the Earth they are observed as magnetic clouds (MC) (e.g. Burlaga et al., 1982). The connection of the auroral spectral characteristics with different types of solar wind streams was studied by several authors (e.g. Hviuzova and Leontyev, 1997, 2001, Sivjee and Shen, 1997). Hviuzova and Leontyev, 1997, 2001 studied the emissions intensities ratio I 6300 /I 5577 that characterizes the hardness of the precipitating electrons spectrum. On the base of a large amount of data (aurora observations at the Loparskaya Observatory during 1970- 1985) the yearly means of the o f aurora intensity ratio were obtained. It was shown that during magnetic clouds aurora with enhanced mean ratio between the red auroral emission (6300 A) and the green one (5577 A) is observed. The precipitating electrons spectrum is extended to the soft electrons region. The spectral characteristics o f the aurora observed during the passage of a recurrent stream are a result of the precipitation of more energetic electrons in the atmosphere and the lack of soft precipitating electrons (with energies <1 keV) (Hviuzova and Leontyev, 1997). The precipitating electrons spectrum is shifted to the higher energies. Sivjee and Shen, 1997 examined the auroral emissions during the solar magnetic cloud (MC) on October 18, 1995. This MC caused a strong magnetic storm (Dst—100 nT). On the base of continuous spectroscopic measurements (about 10 hours) it was shown that a difference between the normal auroras and the magnetic cloud induced ones exists. This difference appears to the precipitations o f electrons with an averaged energy of about 500eV, an event similar to the rare type A global red aurora. In all these papers, the aurora spectral characteristics during long time intervals (during recurrent streams lasting several days, or magnetic clouds lasting tens of hours) were examined. In our paper, the dynamics o f the intensities of the green 5577 A auroral emission and the red 6300 A one during substorms will be studied. In particular, the emissions intensities ratio I 6300 /I 5577 inside the auroral bulge and at its edge will be examined. In order to observe the motion o f substorm bulge, to determine the auroras emissions polar edge o f the bulge and inside it, we used data of high latitude stations. The Auroral Observatory in Longyearbyen is quite a high-latitude station (78.20°N, 15.83°E) and usually substorms are observed more equatorially, from stations at lower latitudes. However, the substorms sometimes reach higher latitudes, normally during high-speed recurrent streams of the solar wind, (e.g. Sergeev et al. 1979, Dmitrieva and Sergeev 1984, Despirak et al. 2008). We selected substorms observed during solar wind high­ speed recurrent streams for our studies. A typical example o f observation of a substorm during a recurrent stream: the substorm onset was at auroral zone latitudes, later it reached high latitude station and moved further to the pole. Thus, we observed the polar edge o f the auroral bulge, when auroras were observed in the station zenith, and inside the bulge, when auroras moved further to the pole. 25