On the effect of geomagnetic field diffusion at the magnetopause

A method is developed to correct the magnetic field of a closed magnetosphere model for geomagnetic field diffusion into the solar wind. The diffusion results in a non-zero normal component of the magnetic field at the inner side of the diffusive magnetopause. The normal component of the magnetic field is estimated to be equal in order of magnitude of B0Rm−1/2, where B0 is the geomagnetic field near the magnetopause, and Rm is the magnetic Reynolds number. A regular magnetic flux from the magnetopause forms a cusp-like region in the dayside polar ionosphere.