Internally Combined Volume-Surface Integral Equation for EM Analysis of Inhomogeneous Negative Permittivity Plasma Scatterers

A well-conditioned internally combined volumesurface integral equation (ICVSIE) for analyzing electromagnetic scattering from perfect electrically conducting (PEC) surfaces coated with negative permittivity plasmas is presented. Existing integral equations pertinent to these problems oftentimes yield ill-conditioned systems of equations. The ill-conditioning stems from the presence of interfaces between a positive permittivity background medium and the negative permittivity plasma and/or is due to low-frequency breakdown. To tackle these issues, the proposed ICVSIE wraps the negative permittivity plasma into a Huygens surface and exploits surface equivalence principles to artificially change the sign of the permittivity of the medium in which equivalent volumetric polarization currents radiate. Next, it combines a Muller combined field integral equation on the Huygens surface with a volume-surface integral equation for the negative permittivity plasma that coats the PEC surface in a manner that circumvents low-frequency breakdown. The accuracy, efficiency, and stability of the proposed ICVSIE are demonstrated via its application to various canonical scatterers and a plasma-engulfed reentry vehicle.