A BOUNDARY-ELEMENT INVESTIGATION OF IRREGULAR FREQUENCIES IN ELECTROMAGNETIC SCATTERING

The paper investigates whether the eigenvalues and resonance frequenci es associated with possible interior standing waves or self-sustaining exterior scattering are irregular frequencies of a new set of integra l equations for electromagnetic scattering recently developed by the a uthors. A quadratic, isoparametric boundary element numerical solution of the integral equations for a dielectric sphere is compared with ex act scattering results obtained from Mie theory. The boundary element solution is shown to give reliable results for these eigenvalues and r esonance frequencies. It is pointed out, however, that the more genera l question of whether other frequencies are irregular for the set of i ntegral equations cannot be resolved hi this way.