Waves In Plasma Sheath Research Articles

The propagation of Alfvén wave in magnetized plasma sheath of hypersonic vehicles in near space

Hypersonic plasma sheath could shield communication signals, which results in the so-called “blackout.” Blackout is a major risk to the safety of re-entry vehicles and cruise hypersonic vehicles in near space. In this study, a propagation model of Alfvén waves in plasma sheaths is developed. The impacts of the external magnetic field, the wave frequency, and the boundary conductivity on the Alfvén attenuation were investigated. According to the simulation results, once the conductivity is close to the Alfvénic conductivity near the onboard antenna, the attenuation of Alfvén waves in the plasma sheath could reach its minimum. The total attenuation of the Alfvén wave in the plasma sheath decreases with the carrier frequency. Also, the attenuation decreases with increasing magnetic field strength.

Analysis of the influence of sheath positions, flight parameters and incident wave parameters on the wave propagation in plasma sheath

The plasma sheath covering hypersonic vehicles has a significant effect on the propagation of electromagnetic waves. Based on the calculation of the flow field of a conical cylindrical, this work studies the propagation of electromagnetic waves in plasma sheath at L-band and Ku-band, and discusses the propagation characteristics in the head, side and tail of the sheath. The dielectric properties of plasma sheath are related to flight speed and altitude. A flight condition corresponds to a unique distribution of dielectric properties. For the conical cylindrical, the results show that flight speed is generally negatively correlated with the transmissivity of the plasma sheath. The reflection characteristics of electromagnetic waves at the L-band and Ku-band when obliquely incident to the plasma sheath show a downward trend. When the frequency is increased to Ku-band, the propagation characteristics of electromagnetic waves in the plasma sheath are related to the position of the sheath.

Research on phase shift characteristics of electromagnetic wave in plasma

The phase shift characteristics reflect the state change of electromagnetic wave in plasma sheath and can be used to reveal deeply the action mechanism between electromagnetic wave and plasma sheath. In this paper, the phase shift characteristics of electromagnetic wave propagation in plasma were investigated. Firstly, the impact factors of phase shift including electron density, collision frequency and incident frequency were discussed. Then, the plasma with different electron density distribution profiles were employed to investigate the influence on the phase shift characteristics. In a real case, the plasma sheath around the hypersonic vehicle will affect and even break down the communication. Based on the hypersonic vehicle model, we studied the electromagnetic wave phase shift under different flight altitude, speed, and attack angle. The results indicate that the phase shift is inversely proportional to the flight altitude and positively proportional to the flight speed and attack angle. Our work provides a theoretical guidance for the further research of phase shift characteristics and parameters inversion in plasma.

Studies on the propagation properties of THz wave in inhomogeneous dusty plasma sheath considering scattering process

The plasma sheath formed during the reentry process is able to block the detection and communication to the hypersonic vehicle. Various of interactions occur during the propagation of EM wave in the plasma sheath. In addition, the dusty particles formed during the ablation of the protective layer make this process more complicated. Dusty plasma sheath is an important factor that affect the detection of hypersonic vehicle. In this work, the propagation properties of THz wave in inhomogeneous dusty plasma sheath are studied. The flow field distribution around the hypersonic vehicle is simulated first. Then the electron density is calculated using equilibrium constant method of the 7-species reacting air model. And the collision frequency is calculated based on the results of the flow field simulation. The absorption and scattering process are studied using scattering matrix method and Mie scatter theory, respectively. The propagation properties are calculated considering the influences of the flight speed, the flight altitude, the radius, the number density and the kind of the ablation particles. The calculation results show that with the increase of THz wave frequency, the transmittance increases firstly and then oscillates. The shape of the transmittance curve is determined by the flight speed, the flight altitude, the radius, the number density and the kind of the ablation particles. The main loss mechanisms in different wave bands has also been discussed and the optimum transition band is given. This work shows that THz wave has good potential applications in hypersonic vehicle detection. It also provides a method to select the optimum detection frequency band.

Study on the Propagation Characteristics of Terahertz Waves in Dusty Plasma with a Ceramic Substrate by the Scattering Matrix Method.

The propagation characteristics of terahertz (THz) waves incident vertically into inhomogeneous and collisional dusty plasma with a ceramic substrate are studied using the scattering matrix method (SMM). The effects of the incident wave frequency and plasma parameters, such as the maximal electron density, dust particle density, dust particle radius and collision frequency, on the reflectance and transmittance of THz waves in the dusty plasma are discussed. In addition, the differences of the propagation properties in the dusty plasma, with and without ceramic substrate, are analyzed. Meanwhile, the differences of the propagation properties in dusty plasma and common plasma, respectively, with ceramic substrate are also compared. Simulation results show that the substrate and dust particles have significant influence on the propagation characteristics of THz wave in plasma sheath. Finally, the transmission increases with the increase of electron density, dust density, dust particle radius and collision frequency.

Analysis of transmission characteristics of THz waves magnetized at different angles in non-uniform magnetized plasma

When a hypersonic vehicle flies, it will have friction with the atmosphere, ionizing the surrounding air, and producing a plasma sheath containing a large number of free electrons. The plasma sheath will cause the electromagnetic wave to seriously attenuate, which will result in communication interruption and other problems. With the gradual realization of terahertz wave technology, its high penetrability and anti-interference performance provides an important way to solve the blackout problem. Thus, the using of the terahertz wave to solve the blackout problem encountered during vehicle reentry is of great significance to studying the transmission performance of terahertz wave in the plasma sheath. This article refers to the public data of the plasma sheath during the reentry of the RAM vehicle. Considering the asymmetry of the sheath density distribution, a double Gaussian distribution is used to simulate the longitudinal electron density distribution. Based on the SMM algorithm, the article uses the magnetization direction, electron density, external magnetic field strength, collision frequency of the non-uniformly magnetized plasma as variables, and their effects on left-hand and right-hand polarized terahertz wave under normal incidence are studied. The results show that these parameters have obvious effects on the transmission performance of terahertz wave in high-density plasma sheath. The right-hand polarized terahertz wave will produce a power absorption peak near the cyclotron frequency due to cyclotron resonance. Changing the magnetization angle in a certain direction will bring an opposite effect on the transmission rate to left-hand polarized and right-hand polarized terahertz wave. Reducing the magnetization intensity can avoid the absorption peak of the right-hand polarized wave by the plasma to a certain extent. Increasing the magnetization can increase the transmission power of the left-hand polarized wave to a certain extent. Moreover, reducing the collision frequency can narrow the absorption band of the right-hand polarized wave in the plasma and increase the transmission power of left-hand polarized wave. In general, the transmission performance of left-hand polarized terahertz wave in non-uniformly magnetized plasma is better than that of right-hand polarized terahertz wave. These results provide a theoretical basis for investigating the blackout phenomenon. The adjusting of these parameters studied in the article is expected to be able to alleviate the blackout problem to a certain extent.

Energy dissipation and power deposition of electromagnetic waves in the plasma sheath

Energy dissipation and power deposition of electromagnetic waves (EMW) in the reentry plasma sheath provide an opportunity to investigate ‘communication blackout’ phenomena. Based on a finite element method (FEM) simulation, we analyze variation of EMW energy dissipation and power deposition profiles dependent on the wave polarization, wave incident angle, plasma density profile and electron collision frequency. Cutoff and resonance of EMW in the plasma sheath are crucial in explaining the regulation of energy dissipation and power deposition.

Propagation characteristics of terahertz wave in plasma sheath around air vehicle

In this paper, the plasma electron density and collision frequency are calculated based on the flow field simulation of RAM C-III air vehicle, and an inhomogeneous plasma model is established according to the calculation results. The effects of plasma density, plasma thickness, plasma collision frequency and external magnetic field on the propagation characteristics of terahertz wave in plasma are analyzed using scattering matrix method. The results show that the propagation loss increases with plasma electron density and plasma thickness, while the transmittance decreases first and then increases with the increasing of collision frequency. When an external magnetic field is applied, the propagation characteristics of the left-handed polarized terahertz wave will be improved, while for the right-handed polarized terahertz wave, the application of magnetic field induces an absorption peak, which shifts to high frequency range with the increasing of magnetic induction intensity. This work may make a contribution to solving the problem of communication blackout.

Propagation characteristics of terahertz wave in hypersonic plasma sheath considering high temperature air chemical reactions

In this work, the propagation characteristics of terahertz wave in the hypersonic plasma sheath is demonstrated and analyzed based on the realistic vehicle model and the high temperature air thermal chemical reactions. Based on the simulated flow field distribution around the hypersonic vehicle, the electron densities of the plasma sheath at different Mach numbers are calculated by adopting the equilibrium constant method of the 7-species reacting air model. And then the propagation model of terahertz wave in plasma sheath is established using the scattering matrix method. The calculated and simulated results show that the plasma electron density is strongly influenced by Mach number, and the higher frequency and smaller incident angle of terahertz wave are advantageous for a better transmittance and lower loss. Furthermore, the effects of an external magnetic field on the propagation characteristics of left-hand and right-hand polarized terahertz wave in plasma sheath are studied. The external magnetic field indeed reduces the transmission loss of the left-handed wave. This work promises that terahertz waves have good potential applications in the detection and the communication for the hypersonic vehicles in plasma sheath.

Study of the Attenuation Characteristic of Electromagnetic Waves in Plasma Sheath

Plasma sheath that seriously impacts the propagation of electromagnetic waves will be produced when an aircraft flying in the atmosphere at very high speed. This thesis concentrates on the study of the attenuation characteristic of electromagnetic waves in plasma sheath. Through discussing the formation mechanism of plasma sheath and analyzing the propagation characteristic of electromagnetic waves, the scope of communication outage will be learned. The plasma sheath is segmented into plentiful subshells which are considered as uniform layers. Ultimately the factors which affect the attenuation of electromagnetic waves will be known.