Study On Nonlinear Effects Of High-power Radio Waves In The Plasma

With the rapid development of Aerospace Technology,the research of communication and control in the plasma near the space has become one of the important and urgent research topic.The characteristics of electromagnetic wave propagation in plasma directly or indirectly to its impact,so the research of the nonlinear effect in the propagation of electromagnetic wave in plasma is also very important.Propagation of electromagnetic wave in plasma is quite complicated,it is influenced by many parameters,the propagation process will produce a variety of nonlinear effects,including self-interaction and interaction and so on.This paper mainly studys two kinds of nonlinear effect,including thermal nonlinear effect and second- harmonic nonlinear effect.In this paper two kinds of nonlinear effect are excited by high-power radio waves.The study has important theoretical significance and application value for the effective use of plasma.Thermal nonlinear effect is due to increased electron temperature after heating,According to the relationship between the collision frequencies and the electron temperature, we can establish a relationship between the medium properties,which includes permittivity and conductivity, and the field. The essence of the thermal nonlinear effect is the relationship between the medium properties and the field.Based on the above, the variety of electron temperature and attenuation constants with the field has been simulated in this paper,and some significant conclusions are obtained.The essence of harmonic nonlinear effect is the production of a new frequency component of the incident electromagnetic wave, the analysis of third-harmonic is more and more complex, and the harmonic effect is not very obvious, therefore this paper mainly analyzes the second-harmonic nonlinear effect.The theoretic basis of the second-harmonic nonlinear effect are fluid motion equation of electrons and ions in the plasma, electron velocity equation and the wave equation of the electromagnetic wave propagates in plasma, which can establish the second-harmonic wave equation of electromagnetic wave propagates in plasma.According to the second-harmonic wave equation, the ratio of the two harmonic field intensity peak to the fundamental field intensity peak can be solved.From the analyzilism of the ratio,we find that thesecond-harmonic field intensity peak will be greater when the collision frequency is bigger and the incident electromagnetic frequency is lower.Inaddition,the simulation results show that the second-harmonic electric field intensity peak is far less than the fundamental field intensity.As the important transmission space,plasma has been widely used in modern scientific practice.In this paper,using the thermal nonlinear effect generated by high power wave propagation in theplasma,combined with the practical application of high power microwave,we got the reflection loss in the nonlinear effects.We also compare with the reflection loss without nonlinear effects.In the end,we got that the nonlinear reflection loss is more than linear reflection loss;the higher the frequency of the incident wave,the greater the reflection loss;the larger the initial collision,the greater the reflection loss.