When a vehicle reenters the earth’s atmosphere at hypersonic speed, the surrounding air molecules are dissociated and ionized by the tremendous heat due to friction with atmosphere, and plasma sheath is formed around the hypersonic vehicle’s surface. The plasma sheath greatly attenuates the electromagnetic (EM) waves radiated from an onboard antenna through reflection and absorption effects, and causes intermittent communication outage. Therefore, the research on the interaction mechanism between the electromagnetic (EM) wave and the plasma sheath is of great significance.
Many studies have been done on the propagation characteristics of EM waves at the plasma sheath. However, only a few researches were focused on the propagations of obliquely incident EM waves on the reentry plasma sheath.
Han Yong Su, a section head at the Faculty of Physical Engineering, has investigated the propagation characteristics of obliquely incident S-polarization EM waves on the reentry plasma sheath by the scattering matrix method (SMM). Assuming the plasma sheath to be nonuniform, unmagnetized, cold, weakly ionized, collisional plasma in steady state, he examined the effects of incident angle, electron density profile and collision frequency on the reflection, transmission and absorption of obliquely incident S-polarization EM wave on plasma sheath.
The numerical results show that when the incident EM wave obliquely passes through the plasma sheath, the amplitudes of reflectance, transmittance and absorptivity are obviously modulated by the incident angle, electron density profile and collision frequency.
In addition, he has found that the transmittance and absorptivity peaks are shifted from the lower to the higher frequency with increasing incident angle, electron density profile and collision frequency.