Numerical Simulation To Study The Propagation Of Waves In Plasmas

This doctoral dissertation has studied the following problems:The application scope of the Poincare-Lighthill-Kuo(PLK)method is suggested by using the Particle-In-Cell(PIC)numerical method.We have studied the head-on collision of two solitary waves.The dependence of the phase shifts after the head-on collision on both amplitudes of two solitary waves is given from our PIC method.It is found that the phase shifts depend on the amplitude of both waves.By using the PIC numerical method,we have calculated the maximum amplitude in the colliding process.The maximum amplitude during the colliding process is approximately equal to the sum of both amplitudes for the small amplitude solitary waves.Comparisons between the numerical results from PIC simulations and the analytical solutions from the PLK method indicate that the both are in good agreement.By using the PIC method,we have investigated the interaction between either a Korteweg-de Vries(Kd V)solitary wave or an envelope solitary wave and a solid boundary.The phase shift is found after reflection of a Kd V solitary wave.It is found that the reflection of a solitary wave at a solid boundary is equivalent to the head on collision between two same amplitude solitary waves.However,there is no phase shift after the reflection of an envelope solitary by the solid boundary.The reflection is different between the Kd V solitary wave and the envelope solitary wave.The maximum amplitude is approximately two times of that of the initial colliding solitary wave.This result is also equivalent to that of the head on collision between two same amplitude solitary waves.The transmission of an electromagnetic(EM)wave in air plasma is studied by Particle-In-Cell Monte Carlo Collision(PIC-MCC)simulation method.The plasmas are assumed to be uniform,collisional and non-magnetized.Each type of species presented in the plasmas is treated by the PIC method,while the electron–neutral collisions are treated by direct Monte Carlo simulation of particle trajectories.Then the dependences of power attenuation of the EM wave on plasma parameters and wave parameters are obtained and discussed.It is found that power attenuation of the EM wave is strongly affected by the plasma density,density of neutral gas and the frequency of the EM wave.The EM wave power attenuation increase with the increase of electron density,while the EM wave power attenuation decreases as the EM wave frequency.The EM wave power attenuation decreases as the neutral gas density increases.The propagation properties of EM waves in dusty plasma of rocket exhaust are studied.Usually,the dust sizes are different in a general dusty plasma,however,most of the previous research works only investigate the mono-sized dusty plasma.The effects of dust size distribution on the EM wave attenuation of dusty plasmas have been investigated.The dependences of the EM wave attenuation on the electron density of dusty plasmas,density of neutral gas and the frequency of the EM wave are obtained and discussed.It is found that the EM wave attenuation is much smaller for the THz wave than that of the GHz wave,and it decreases monotonously as the frequency of the EM wave increases.The results illustrate that the EM wave attenuation constant have a maximum value when the electron-neutral particles collision frequency is close to the EM wave frequency.The EM wave attenuation constant increase with the increase of electron density and dust particles density.Moreover,the EM wave attenuation constant decreases as the dust size decreases for a mono-sized dust particles.The smaller the dust size,the smaller the EM wave attenuation constant.It indicates that the attenuation of the EM wave is mainly determined by the largest dust particles.Finally,we conclude that the larger the dust particle,the stronger the attenuation to the EM wave.