Model of the magnetic field in the inner heliosphere with regard to radial field strength leveling in the solar corona

On the basis of experimental results from the Ulysses spacecraft, a model is proposed for calculating the magnetic field in the corona and the heliosphere in the potential approximation, which is a modification of the potential-field source-surface model. In addition to the photospheric surface and the source surface, a new demarcated spherical surface (leveling surface) is introduced in this model. The magnitude of the radial component of the magnetic field on this surface is assumed to be constant, and its sign abruptly changes from one hemisphere to another. General analytical formulas are given to calculate the potential and field for this model. Calculations are described in detail using the dipole and quadrupole harmonics as examples. Expressions are obtained for the surface currents. The results of visualization of the magnetic field for an axial dipole are discussed.