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.

T.A. Yahnina and A.G. Yahnin The isotropy boundary latitudes were averaged for every subset o f the events (magnetic clouds with southward Bz, fast recurrent streams, Sheath, CIR) separately for minimum and maximum o f the solar activity. Results and discussion The number of selected events for the four subsets is presented in Tables 1 and 2. Entries on these Tables are, also, averaged parameters of the considered solar wind streams. The MLT variation o f the isotropy boundary latitude is plotted in Figure 1. Plots for 1996 and 2001 are shown on the left and right, respectively. The line 1 is the averaged Table 1. Mean solar wind parameters for 1996 and some selected solar wind stream intervals____________ Number of events Bz mean (nT) N mean (cm'3) V mean (km/s) P mean (nPa) (1) Whole year -0.16 7.89 425 2.4 (2) RS 13 -0.34 3.56 565 2.3 (3) CIR 10 -0.71 12.61 417 4.3 (4) Sheath 10 -2.39 20.44 407 6.5 (5) MC (Bz<0) 5 -7.11 8.46 403 2.5 Table 2. Mean solar wind parameters for 2001 and some selected solar wind stream intervals Number of events Bz mean (nT) N mean (cm'3) V mean (km/s) P mean (nPa) (1) Whole year -0.37 6.10 422 2.2 (2) RS 9 0.27 3.11 566 1.7 (3) CIR 13 0.83 14.53 403 4.3 (4) Sheath 13 0.78 22.49 479 10.1 (5) MC (Bz<0) 6 -8.70 4.68 452 1.9 IB for whole years 1996 and 2001 independently on the type o f the solar wind stream. The line 2 represents recurrent streams influence on the magnetospheric state (configuration). Lines 3-5 are the averaged IB latitudes as function of MLT for CIR, Sheath, and southward Bz part o f magnetic clouds. The Figure clearly demonstrates that every kind of considered solar wind fluxes produces a distortion o f magnetotail from an average state. The strongest magnetotail stretching is observed during magnetic clouds with Bz < 0. Indeed, southward Bz strongly affects the IB latitude (Yahnina et al., 2005). The weakest magnetic field distortion is found for high-speed recurrent streams. Evidently, this distortion relates to large values of V, while Bz is variable, and averaged Bz is about zero (see Tables 1 and 2). The enhanced magnetotail stretching during both CIR and Sheath events relates, probably, to increased density (and dynamic pressure). The stronger effect of Sheath is, likely, due to the higher (in comparison with considered CIRs) plasma density. (Note that mean values presented in Tables differ from those obtained by Yermolaev et al. (2009), who used much larger statistics, but did not separate minimum and maximum o f solar activity and did not divide magnetic clouds into intervals with negative and positive Bz). Figure 1. Latitude o f the proton isotropy boundary as function o f MLT for different solar wind conditions. 104