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.

Magnetotail stretching under different solar wind conditions As mentioned, the line 5 in Figure 1 represents only that part of the magnetic clouds, which contains southward Bz. The latitude of the isotropy boundary corresponding to the magnetic clouds (or their parts) with northward Bz is higher than the line 1 (not shown). It is worth to note that the IB latitude averaged through the year is lower for 2001 than for 1996 (see, also, Yahnina et al., 2005). It holds for every type o f the streams as well. The reason is not clear yet. It is possible that it is a consequence of the limited statistics used in this study. Let us discuss the differences of the isotropy boundary location related to different solar wind streams in the context of substorms. Sergeev et al. (1983) (see, also, Yahnin (2008)) on the basis of comparison of the auroral onset with the electron isotropy boundary argued that substorms start in the magnetotail at stretched field lines (namely, in the region where the value o f the magnetic field is only few nT). Decrease o f the isotropic boundary latitude means stronger stretching o f the field lines. In turn, this means that the region o f weak magnetic field approaches the Earth. Besides, as mentioned in Introduction, the low-latitude IB location relates to longitudinal expansion of region of the weak magnetic field (Newell et al., 1998). Thus, one can expect that during magnetic clouds the region where substorms start is closer to the Earth, and the substorms is to develop in a wider longitudinal region than during other solar wind structures. Indeed, Henderson (2004) and Henderson et al. (2006) found that during magnetic clouds the substorm activity (stretching, dipolarization, particle injections, NENL formation, etc.) occurs and is sustained at locations extremely close to the Earth. Henderson (2004) and Pulkkinen et al. (2006) noted the wide azimuthal range of dispersionless injection activity during magnetic clouds, and Despirak et al. (2009) stressed that the ratio of the longitudinal dimension o f the auroral bulge to its latitudinal expansion is larger during magnetic clouds than other types of the solar wind streams. A cknow ledg em en ts. We express our gratitude to P. Newell and other members of the Auroral Particles and Imagery Group at JHU/APL for making the DMSP particle precipitation data available for the community, to R. Lepping and members o f the WIND MFI team for providing online the list of the magnetic clouds observed by the WIND spacecraft, and to O. Maris and G Maris for catalog of the high speed solar wind streams. The work is performed in frames of the basic research programs № 4 of the Presidium of the Russian Academy of Science (RAS) and № VI. 15 “Plasma processes in the solar system” of the Division of Physical Sciences of RAS. References Burlaga, L.F. et al., A magnetic cloud and a coronal mass ejection. Geophys. Res. Lett., V.9, 1317-1320, 1982. Despirak I.V., A.A. Lubchich, A.G. Yahnin, B.V. Kozelov, and H.K. Biemat, Development of substorm bulges during different solar wind structures. Ann. Geophys., 27, 1951-1960,2009. Henderson, M.G. (2004), The May 2-3, 1986 CDAW-9C interval: A sawtooth event, Geophys. Res. Lett., 31, LI 1804, doi: 10.1029/2004GL019941. Henderson, M.G., et al. (2006), Substorms during the 10-11 August 2000 sawtooth event, J. Geophys. Res., I l l , A06206, doi:10.1029/2005JA011366. Lvova E.A., V.A. Sergeev, G.R. Bagautdinova. Statistical study of the proton isotropy boundary. Ann. Geophys., V.23, 1311-1316, 2005. Newell P.T., V.A. Sergeev, G.R. Bikkuzina, S. Wing. Characterizing the state of the magnetosphere: testing the ion precipitation maxima latitude (b2i) and the ion isotropy boundary. J. Geophys. Res., V.103, 4739-4745,1998. Newell P.T., Y.I. Feldstein, Yu. I. Galperin, C.-I. Meng, The morphology of nightside precipitation. J. Geophys. R es.,V . 101, 10737-10748,1996. Pulkkinen, T.I., Ganushkina, N.Y., Tanskanen, E.I., Kubyshkina, M.V., Reeves, G.D., Thomsen, M.F., Russel, C.T., Singer, H.J., Slavin, J.A., and Gjerloev, J.: Magnetospheric current systems during storm-time sawtooth events, J. Geophys. R e s, 111, A l 1S17, doi:10.1029/2006JA011627, 2006. Sergeev, V. А , М. V. Maikov, and K. Mursula, Testing of the isotropic boundary algorithm method to evaluate the magnetic field configuration in the tail, J. Geophys. Res., 98, 7609, 1993. Sergeev, V .A , A.G. Yahnin, and R.J. Pellinen, Relative arrangement and magnetospheric sources of zones of energetic electron injection, diffuse and discrete auroras during the preliminary phase o f a substorm, Geomagn. Aeron., 23, 972-978,1983. Yahnin A .G , Magnetospheric Substorm: Main features and possible mechanisms. In: Plasma Heliophysics (eds. L.M. Zelenyi and I.S. Veselovsky), Moscow, Fizmatlit, pp. 465-483,2008. Yahnina T .A , A.G. Yahnin, D.A. Yahnin, P.T. Newell, and T. Sotirelis. Long-term behaviour of the magnetotail stretching. “ Physics o fAuroral Phenomena”, Proc. XXVIII Annual Seminar, Apatity, pp. 78-81, 2005. Yermolaev Y u.I, Nikolaeva N .S , Lodkina I.G , Yermolaev M.Yu . Catalog of large-scale solar wind phenomena during 1976-2000. Cosmic Research. V.47, № 2, 81-94, 2009. 105