Surface magnetic charge densities and demagnetizing factors for rotating astroids

Abstract

The cusp characteristics are investigated for a rotating astroid placed in an axially uniform magnetic field. The rotating astroid has point and line cusps. The surface magnetic charge densities are numerically calculated by the surface magnetic charge simulation method, modified for the rotating astroid. The results are illustrated for various relative permeabilities /spl mu/. The numerical results show that the charge densities concentrate with a peak in vicinity of the point cusps for /spl mu/>1 and in vicinity of the line cusps for /spl mu/<1. At the point cusps, the charge densities become zero in the cases of /spl mu/</spl infin/ and become infinite in the case of /spl mu/=/spl infin/. To make clear the characteristics of the charge densities near the cusps, the slope factors are defined and evaluated for 0/spl les//spl mu//spl les//spl infin/. In addition, the partial, fluxmetric, and magnetometric demagnetizing factors are evaluated by using those numerical results of the charge densities for 0/spl les//spl mu//spl les//spl infin/. It is shown that the partial demagnetizing factor becomes negative near the point cusps for /spl mu/</spl infin/. This reason is explained in terms of the demagnetizing field.