Statistical multipole expansion and its application to an arbitrary shielding geometry with small variations

The statistical multipole expansion is a compact representation of a stochastic electromagnetic field in terms of the statistical moments of the corresponding multipole amplitudes. The paper deals with a systematic approach to obtain the statistical multipole amplitudes of the electromagnetic field inside an arbitrary shielding geometry by means of a spherical-multipole interface. The numerical evaluation is performed for a box-shaped metallic shield with a rectangular aperture, the size of which is known only in terms of its statistics.