The dispersion of terahertz signals propagating in a hypersonic plasma sheath under a time-varying magnetic field

This paper investigates the dispersion relation of terahertz waves propagating in a hypersonic plasma sheath under a low-frequency, time-varying magnetic field. A theoretical model is developed, deriving an effective dielectric tensor and modified dispersion relations for the Ordinary (O) and Extraordinary (X) modes. An analysis reveals that the magnetic field significantly alters the X-mode dispersion, introducing an effective gyrofrequency ωc/2 that reduces wave attenuation, particularly in high-density plasmas. In contrast, the O-mode remains unaffected. This study demonstrates that manipulating the dispersion relation via a time-varying magnetic field provides a viable mechanism for mitigating communication blackout.