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.

А. V. Nikolaev et al. Fig. 6a View from North. R1 and R2 loop locations Fig. 6b Ionospheric projections of the strips drawn in fig. 6a obtained in XY plane. Colored strips indicate traced structures with (colored lines) and without (black lines) addition of SCW2L model, similar in morphology with BBFs. Model parameters are similar to those presented in fig. 3. Conclusions We quantitatively described the magnetospheric magnetic field deformations for the set of basic SCW2L parameters in a simple symmetric geometry. The substorm current wedge two-loop configuration and its parameters approach does not provide complete information about auroral structures or about magnetospheric field distortions during real magnetospheric substorm, but gives an idea of the amplitudes o f ionospheric footprints displacement for different activity levels and predicts common forms of active aurora. We found, that the R1 loop intensity is the most effective parameter, which strongly contributes ionospheric footprints shifts. The latitudinal displacement may reach ALat ~ 9° CGLat during rare and strong substorms, do not exceed ALat ~ 5-6° CGLat in moderate and minimizes ALat< 3°CGLat during low-level disturbances. This estimations are consistent with earlier predictions by Vasilyev et al., [1986], who showed that amplitude of auroral bulge expansion for current intensities I) = 1 MA approximately 7° CGLat. In terms of SCW2L model difference in two degrees can be explained by R2 loop which depress dipolarization attributed to R1 loop. As for magnetic effects related to R2 loop, they slightly change ionospheric positions of neutral sheet points located in vicinity of R2 equatorial current, this change do not exceed ALat ~ 2° CGLat in equatorward direction. The neutral sheet footprints, changing their ionospheric locations due to SCW, forms auroral bulge structure. This effect was first noticed by Vasilev et al., [1986] on a basis of a simple wire-like SCW model. Moreover, helical magnetic field existing near FACs leads to a twisting of magnetic field lines as a result, appearing WTS bends at the dusk and dawn side boundaries o f the auroral bulge. Such ionospheric pattern caused by magnetic field reconfiguration can be used as a natural explanation of substorm manifestation in high- latitude active aurora. References Henderson, M. G. (2012) Auroral Substorms, Poleward Boundary Activations, Auroral Streamers, Omega Bands, and Onset Precursor Activity, in Auroral Phenomenology and Magnetospheric Processes: Earth And Other Planets (eds A. Keiling, E. Donovan, F. Bagenal and T. Karlsson), American Geophysical Union, Washington, D. C. doi: 10.1029/2011GM001165. Henderson, M. G., J. S. Murphree, G. D. Reeves (1994), The activation of the dusk-side and the formation of north-south aligned structures during substorms, in proceedings of the Second international Conference on substorms (ISC-2), edited by J. R. Kan, J. D. Craven, S. Akasofu, p. 37, Geophys. Inst., Univ. Alaska, Fairbanks. Lyons, L. R., Nishimura, Y., Xing, X., Shi, Y., Gkioulidou, М., Wang, С.-Р., Kim, H.-J., Zou, S., Angelopoulos, V. and Donovan, E. (2012) Auroral Disturbances as a Manifestation of Interplay Between Large-Scale and Mesoscale Structure of Magnetosphere-ionosphere Electrodynamical Coupling, in Auroral Phenomenology and Magnetospheric Processes: Earth And Other Planets (eds A. Keiling, E. Donovan, F. Bagenal and T. Karlsson), American Geophysical Union, Washington, D. C.. doi: 10.1029/2011GM001152. Nakamura, R., T. Oguti, T. Yamamoto, S. Kokubun (1993), Equatorward and poleward expansion of the auroras during auroral substorms, J. Geophys. Res., 98(A4), 5743-5759. Sergeev, V. A., L. I. Vagina, R. D. Elphinstone, J. S. Murphee, D. J. Hearn, M. L. Johnson (1996), Comparison of UV optical signatures with the substorm current wedge predicted by an inversion algorithm, J. Geophys. Res., 101, P. 2615-2627. Sergeev, V. A., N. A. Tsyganenko, М. V. Smirnov, A. V. Nikolaev, H. J. Singer, and W. Baumjohann (2011), Magnetic effects of the substorm current wedge in a 'spread-out wire' model and their comparison with ground, geosynchronous, and tail lobe data, J. Geophys. Res., 116, A07218, doi: 10.1029/2011JA016471. Tsyganenko, N.A. (1989), A magnetospheric magnetic field model with warped tail current sheet, Planet. Space Sci., 37, 5-20. Vasilyev, E. P., М. V. Maikov, V. A. Sergeev (1986), Three-dimensional effects of Birkeland's current loop, Geomagn. And Aeronomy, V. 26, P. 114, №1. 54