Numerical Investigation On The Nonlinear Problems Of Hpm Pulses Propagation Through The Atmosphere

The propagation and breakdown mechanism of High Power Microwave (HPM) pulse is researched in this dissertation. Taking into account the characteristics of HPM atmosphere propagation model and the efficiency of previous similar studies, the finite-difference time-domain (FDTD) method is employed to simulate the HPM atmospheric propagation model. By this approach, the law of atmospheric propagation of high power microwave pulse is revealed and an important reference for high power microwave pulse propagation and engineering applications is given.At first, the application background of the HPM pulse is reviewed, and the basic principles of FDTD are briefly introduced. Meanwhile, the FDTD difference schemes for high-power microwave atmospheric propagation model and the characteristics of HPM propagation and breakdown are introduced.Combined with the physical meaning of high power microwave atmospheric propagation and the strict mathematical proof, the stability condition of the FDTD difference schemes for high-power microwave atmospheric propagation model is derived, as well as the corresponding numerical dispersion is analyzed. The numerical results show the FDTD method has a good feasibility and validity in dealing with the issue of high-power microwave atmospheric propagation, and has a higher computational efficiency compared with other methods. By analyzing the breakdown conditions of high-power microwave, the breakdown threshold is estimated. The estimation results and FDTD results and experimental data are consistent. The estimation results of breakdown threshold can provide important reference for high-power microwave engineering applications and related experiments.To further enhance the simulation efficiency of high-power microwave atmospheric propagation, a new approach, that is, subsection FDTD method is proposed. The method is realized by separating computation space and transferring the data between each subsection, which directly based on the traditional FDTD algorithm. The proposed method improves the simulation efficiency of high-power microwave pulse long-distance propagation. At the same time, its high efficiency provides a solid technical support for the issue of the ultra-wideband high power microwave pulse atmospheric propagation.By solving the effective E field strength of the ultra-wideband HPM atmospheric propagation, the parameters of ultra-wideband high power microwave interacts with the atmosphere can be obtained. And combined with the improved subsection FDTD method, the specific process of ultra-wideband HPM atmosphere propagation is calculated. The propagation process of the atmosphere, tail erosion effect and other non-linear physical problems of Gaussian pulse, modulated Gaussian pulse, differential Gaussian pulse, damped sine wave such as ultra-wideband high power microwave pulse are studied, and the inference of air breakdown to its spectrum is analyzed. At first, the electron density evolution due to the HPM pulses and the reaction to HPM pulses caused by electron density evolution is studied. And then the mixture-atmosphere which is composited by plasma and non-plasma can be layered as inhomogeneous medium. Finally, the reflection characteristics of the HPM propagation in the mixture-atmosphere are investigated by FDTD in inhomogeneous medium.A semi-analytical model for the propagation of the repetition frequency HPM pulses is established. And a critical repetition frequency for the HPM pulse is presented. As well as the breakdown threshold of the repetition frequency HPM pulses is derived. Fianlly, the effects of different parameters of the repetition frequency HPM pulses on air breakdown are analyzed.At last part of the dissertation the study of propagation mechanism of HPM pulse is summarized, and the development directions of these researches are predicted.