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.

model magnetic field vectors and the geographic coordinates of the mapping along geomagnetic field lines from the satellite positions to an ionospheric level of 400 km. On average, the ДВ (T01) value amounts to about 5.6 nT, ДВ (T96) to about 4.6 nT, while ДВ (PM) is near ~14.8 nT and almost everywhere in the positive range. The number of cases where ДВ is smaller for В (T01) than for В (T96) is 3 versus 7 with the inverted ratio. The average difference of the mapped geographic latitude positions using T01 and T96 is 0.72° and its longitudinal spread is 2.46°. The corresponding values for a comparison between the T01 and PM models are 2.46° in latitude and 14.3° in longitude, respectively. For some particular cases during geomagnetically disturbed conditions, the latitudinal difference of the mapped footpoints attains 3 5°. Models o f the geomagneticfield and magnetometer measurements o f Cluster FGM in the magnetospheric tail Conclusions The compilation o f magnetic field data, measured by FGM on board the Cluster satellites compared with T01, T96, and PM model values, mapped from the tail side magnetosphere into the ionosphere, shows the following: 1. The smallest deviations on average from the measured magnetic field in the magnetospheric tail is obtained by the T01 model. During the geomagnetically quiet example day it reaches -4.2 nT, while it gains -5 .6 nT and -9.5 nT for T96 and PM, respectively. The corresponding values for the disturbance day are -10.9 nT (T01), -16.0 nT (T96), and -18.8 nT (ПМ). The best coincidence between measured and modelled tail magnetic field magnitude values is therefore obtained with the T01 model. 2. During disturbance intervals all three models concur in the fact, that the difference between observed and modelled magnetic field values is of the order o f -20 nT, but closer to perigee it grows to -4 0 nT. 3 The mapping of satellite values from the magnetosphere into the ionosphere by use of the T01 and the T96 model differs on average by 0.72° in latitude and 2.46° in longitude. Comparing T01 and PM, the corresponding average values are 2.46° in latitude and 14.3° in longitude, increasing to 3°- 5° in latitude during disturbance intervals. 4. It would be very useful to have independent criteria, which allow to estimate the precision o f the mapping along magnetic field lines from the magnetosphere into the ionosphere. A cknow ledgm en ts. This study is supported by the Deutsche Forschungsgemeinschaft (DFG), the RFBR grants 08- 05-00896, and the Norwegian Research Council. 1 0 - 1 1 August 2 0 0 7 1 9 - 2 0 August 2 0 0 6 L \ i г Л " ч Г < 1HI 1 23:00 04:16 09:36 14:55 20:15 UT 02:40 09:05 15:45 22:14 01:54 UT 10 0 -10 23:00 04:16 09:36 14:55 20:15 UT 23:00 04:16 09:36 14:55 20:15 UT 23:00 04:16 09:36 14:55 20:15 UT 02:40 09:05 15:45 22:14 01:54 UT Figure 2. Variations of the IMF By and Bz components, the dynamic pressure Pdyn of the solar wind, and of the geomagnetic activity indices ASY-H, Sym-H, AU and AL for the interval of 10-11 August 2007 (left) and 19-20 August 2006 61