Propagation Characteristics Of Electromagnetic Waves In A Dusty Plasma

In space,substances mostly exist in the plasma state.Over 40 metric tons of dust of meteoric origin eneters the Earth’s atmosphere every day,so a state of coexistence of plasma and dust formed in earth orbit space is called dusty plasma.It changes the near-earth space electromagnetic environment,an imponderable impact on space communication,such as Polar mesospheric summer echoes(PMSE),Noctilucent clouds(NLC).Meanwhile,dusty plasmas in reentry vehicle communications,microwave attenuation in rocket exhaust,and industrial manufacturing field also has important application value.Among the numerous applications,electromagnetic wave propagation through dusty plasma has been studied most extensively in recent years,mostly due to direct relevance to plasma diagnostics,space exploration,reentry physics,and broadcast communication.At present,many researches about the interaction between electromagnetic wave and dusty plasma focus on dust acoustic wave,ion acoustic solitary wave,dust ion acoustic shock wave,etc.but there is lack on systemic simulation of transmission characteristics of microwave.Th is study systematically investigates the relationship between transmission characteristics of microwave and parameters of dusty plasma through theoretical derivation,simulation and experimental validation method.Based on the theory of interaction between dust particles and plasma,combined with dynamic theory,this paper derives the permittivity of weakly collisional and fully ionized,weakly ionized dusty plasmas.Weakly collisional and fully ionized dusty plasma is a new model.In the absence of the existence of the neutral molecules,so the electronic-ion collisions directly determine the loss of the electromagnetic energy.However,in weakly ionized dusty plasmas,a large number of neutral gas molecules are not ionized,so the collision between electrons and neutral molecules determines the transmission characteristics of elect romagnetic waves.The transmission models of electromagnetic waves in fully ionized and weakly ionized dusty plasmas are established,respectively.By using the transmission model of three-layer-medium,the relationships between reflection coefficient,transmission coefficient,absorption coefficient and the charge,the radius,the concentration of dust grains have been gotten.The influences between fully ionized and weakly ionized dusty plasmas on the electromagnetic wave transmission are different,which indicate that the collision frequency is the main factor that affects the transmission of the electromagnetic wave in the dust y plasmas.Combined with the hollow cathode discharge plasma generation device in laboratory,a vibration mesh is used to achieve low pressure dust particles injection into the device,and forming a stable dusty plasma environment.The whole numerical simulation is built by COMSOL Multiphysics platform and the simulation conditions are set according to the conditions of the laborato ry plasma generation device.Simulations are carried out before and after input of dust particles into plasma.Under the conditions studied showed a decrease in electron density caused by input of dust nanoparticles.At the same time,the parameters of the dusty plasma are measured by Langmuir probe,and the changes of electron density and electron temperature before and after the injection of dust particles were observed.The measured results were in agreement with the simulated results.The dust particles are negatively charged by colliding with electrons and ions,which result in the reduced electron density.The characteristics of electromagnetic wave propagation in dust y plasma are studied by using vector network analyzer and corresponding microwave antenna,and compared with numerical simulation results.By changing the density of the dust particles and the ionized gas composition,pressure and discharge power in the discharge chamber,the electromagnetic parameters of the dust y plasma in different cases are measured.The basic parameters of the electromagnetic wave transmission characteristics in the dusty plasma are analyzed,and the transmission law of the electromagnetic wave in the dusty plasma is obtained.The results show that the physical properties of charged dust particles and the discharge environment of dust y plasma have an effect on the transmission of electromagnetic waves.By the study of the paper,the influence of the dust grains in dusty plasma can’t be ignored.The results can be used to solve the attenuation of rocket plume on microwave,the phenomenon of blackout and the phenomenon of PMSE.