CFAB QUADRUPOLE TERMS IN MAGNETIC SINGULARITY IDENTIFICATION

In magnetic singularity identification (MSI) of coonducting and permeable scatterers one considers the low-frequency poles with real natural modes and frequencies to represent the magnetic-polarizability dyadic. This is an approximation neglecting the higher-order multipoles. This paper considers the magnetic quadrupole terms as a correction to the dipole-only representation. This leads to the concept of the effective center of a natural mode to minimize the quadrupole contribution. In the case of scatterers with certain symmetries there can also exist natural modes with no magnetic-dipole contribution, but with a quadrupole contribution. One potential use of a quadrupole information is in removing orientation ambiguities of the visually obscured scatterer