A Magnetic Field-Independent Absorbing Boundary Condition for Magnetized Cold Plasma

Abstract—An effective absorbing boundary condition (ABC) based on the second-order approximations of Engquist and Majda’s wave equations is presented for terminating three-dimen-sional finite-difference time-domain (FDTD) models employing the E-J collocated magnetized cold plasma algorithm. Numerical tests demonstrate that this ABC can effectively terminate magnetized plasma models involving arbitrary and spatially varying directions of the background magnetic field, a capability that is not provided by the recently developed KPML or NIMPML for magnetized cold plasma. This new capability will permit implementation of the Engquist and Majda-based ABC of this letter into localized and particularly global FDTD models of the Earth–ionosphere system involving varying directions of the magnetic field throughout the grid. An accuracy and stability analysis of this ABC is presented. Reflection errors are shown to be consistently less than 5 % for various magnetic field directions and for magnetized plasmas having different electron densities by incorporating the phase velocity calculated at the center frequency of the source spectrum into the ABC formulation. Index Terms—Absorbing boundary conditions (ABCs), electro-magnetic propagation in plasma media, finite-difference methods, ionosphere, plasmas. I