ИСТИНА

The azimuthal magnetic field component in the magnetotail By (in the east-west direction) is mainly determined by a similar component of the interplanetary magnetic field and magnetosphere dynamics. According to the observations of the Geotail project 1995-2005 we formed the database to analyze the impact of various factors on the magnetospheric Bym field. In this work we consider different models of the Bym as well as contributions of certain physical factors to the Bym for differing values of Bzi. The results show that the regression coefficient between Bym and Byi depends on the choice of a set of conditions for data analysis. A set composed only for satellite intersections of equatorial plane, includes more measurements madeat the southern interplanetary field, when the tail configuration is always changing. Set, consisting of long intervals of plasma sheet (equatorial zone) includes more measurements made in magnetically quiet period.