On the three-dimensional structure of the solar magnetic field in interplanetary space

The three-dimensional structure of the solar magnetic field in the interplanetary space is inferred from a theoretical point of view. We use the magnetic field produced by a magnetic dipole rotating obliquely in vacuum. The correction for the presence of a plasma surrounding the Sun is taken into account in terms of a phenomenological approximation.Our method well reproduces the basic features of the polarity-reversal-surface (the neutral sheet in the two-hemisphere model by Saito (1975)) obtained on the basis of observational data, i.e. the snail-shell like structure and variation of its precise shape in accordance with the solar cycle, except for the folding of the surface.