FDTD Simulation of Terahertz Wave Propagation in Time-varying Plasma

Air ionization and heat shield ablation generate a plasma sheath around vehicles during hypersonic reentry or entry. Terahertz (THz) waves (0.1-10 THz) are much easier than millimeter waves to propagate through plasma with electron density up to 10
²⁴
m
^-3
. The Finite Difference Time Domain (FDTD) methods have been successfully applied to many electromagnetic (EM) problems, including issues in plasma for its accuracy. In this paper, FDTD method is used to analyze the terahertz wave propagation in time-varying plasma. The current density in plasma is assumed to be located at the center of the Yee cube. Finally, the FDTD equations for the current density are derived from Maxwell's equations and constitutive relation. In the simulation, a time-varying and spatially inhomogeneous plasma is considered. The electron number density profile of the plasma is assumed to be the linear profile. The plasma is divided into a series of layers. The electron density in each layer varies with time in different forms. The power attenuation characteristic of different time-varying forms are calculated with FDTD method. The overall power attenuation with time are analyzed for different plasma and signal parameters, such as the electron density, the collision frequency, the signal frequency and so on. Using FDTD method, other kinds of plasma, such as magnetized plasma and thermal plasma. Therefore, simulations of scattering characteristics of complex equipment in dynamic and inhomogeneous plasma will be meaningful work in the future.