On the use of the geomagnetic field approximation by the eccentric dipole in problems of ionosphere and plasmasphere modeling

The relationships for the transformation of the geographic coordinates of a ny point into eccentric field coordinates of this point and vice versa with out intermediate calculations have been presented. Similar relationships ha ve been obtained for the components of the eccentric-dipole magnetic field. The specific features of the structure of the equations for the ionospheri c plasma during the geomagnetic field approximation by the eccentric dipole are discussed. This can promote a wider use of such an approximation in th e study of the ionosphere and plasmasphere.