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.

“P hysics o f Auroral P henom ena”, Proc. XXXIII A n n u a l Sem inar, A patity, pp. 95 - 98, 2011 © Kola Science Centre, Russian Academy of Science, 2011 Polar Geophysical Institute SOLAR WIND RECURRENT PHENOMENA IN 23-th MINIMUM T.E. V al'chuk (Pushkov Institute o f Terrestrial Magnetizm, Ionosphere and Radio Wave Propagation RAS, Moscow reg., Troitsk, e-mail: valchuk(a),izmiran. ru) Abstract. The prolonged minimum of solar activity (SA) in the end of 23-th solar cycle is continuing now. Very low level of SA and geomagnetic disturbance is observed in the beginning of 2010. The phase of sunspot minimum is suitable for investigation of long-lived phenomena o f SA, especially heliosphere plasma layer (HPL) and connected with him sector structure of interplanetary magnetic field (IMF) on the Earth’s orbit. Recurrence of fast solar wind (SW) flows is the feature of regular phenomena, connected with equatorial and near-equatorial coronal holes (CHs) in minimal phase of SA. Namely these CHs are producing high-speed SW in immediate proximity to HPL. Absence of sporadic phenomena o f SA (such as flares, coronal mass ejections and filaments) allows us to study SW and plasma parameters (data Wind) in the near-Earth cosmic space in quiet condition on the Sun. For these purposes the interval of Carrington rotations №2052-2091 (from January, 2007 till January, 2010) is defined. Fractal dimension calculations help us to estimate structural variations on intervals, which are lasting about a week or more. Such intervals have been named “activity impulses” in classical works of M.N. Gnevyshev and A.I. O ’l. In an initial phase of a minimum these activity impulses have concrete manifestations: the high-speed recurrent streams of SW from equatorial and near- equatorial CHs. Impulses are separated by the regions o f sector structure transition boundaries in according with heliosphere plasma layer intersection. It allows us to investigate long-lived phenomena of SA and to explain changes by means of transformations o f general solar magnetic field, large-scale magnetic fields and local photospheric magnetic fields in minimum. Comparison with solar maps, such as WSO source surface field, WSO photospheric magnetic field and coronal holes, helps us in SW flows - to recognize reliable source on the solar disk. A brief summary includes: 1. Fast solar wind streams from local equatorial coronal holes o f minimum generate activity impulses. 2. Recurrence and variability of activity impulses are caused by heliophysical reasons, such as large-scale magnetic field transformations and reorganization of CHs in near-equatorial belt of the Sun. 3. Effect of the helio-projection o f the Earth on the solar disk in yearly motion is seen in the preferred polarity of sector structure in Carrington rotations, which including equinoctial points. 4. Fractal dimension calculations confirm the plasma layer transitions on the Earth’s orbit. 5. Low geomagnetic activity exists in minimum. The growth over quiet level is produced by activity impulses. 6 . The duration of 23-th minimum is connected with the reaching of SA secular minimum, such as in the beginning o f the twentieth century. 1. Introduction Recurrent phenomena in the geomagnetic disturbance were studied actively since 30-th years o f the XX century [1- 3], in IGY period and after formation of Data Centers A and B. The connection of 27-days magnetosphere recurrence phenomena with sources on the Sun is investigated statistically [4] and specifically on large quantity of examples. First of all, the role of high-speed solar wind (SW) streams as the reasons of the geomagnetic activity growth was recognized. Then high-speed streams of SW have been in turn classified on types depending on sources on the Sun and in accordance with SW parameters on the Earth orbit. These parameters were measured by cosmic instruments in near-Earth space, and subsequently in a heliosphere by means o f Ulysses, INTERBOL, Mars - Odysseus missions. Characteristic examples of sporadic flare events (connected with active regions (AR) on the Sun) and also with coronal mass ejections - possess individual signs, their generation originates from solar AR’s. Time o f AR life is estimated as one Carrington rotation or several ones sometimes. Presence of so-called active longitudes on the Sun promotes to AR "reproduction" in places of their former existence. It complicates a situation in addition, but their repeatability concerns with AR life only. All these phenomena are the sporadic events. The expressed repeatability of the recurrent events allocated in separate type is estimated in many Carrington rotations of the Sun [5]. Recurrent phenomena are generated from long-living SW streams from coronal holes. This concept is today the basic. However, nature o f CHs as sources of fast SW it is not understood up to the end - problem in solar physics is not closed, since the mechanism of SW generation from CH is not established. The localization of CHs on a disk is studied: polar CHs in minima of solar activity became the most known experimental fact. Variations of CHs in average and low heliolatitudes are in a studying stage nowadays. We study the reasons of their occurrence and migrations, fast changes of contrast and borders of CHs and properties o f SW streams from CHs too. 95