高温等离子体中太赫兹波的传输特性
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摘要
通过解析方法研究了高温等离子体的太赫兹波传输特性.研究发现,高温等离子体对太赫兹波高频频段透过率较高,表现为通带;对低频频段透过率较低,表现为阻带.这与冷等离子体中电磁波的传输特性是一致的.但其透射率还受到温度与磁场的影响,当改变高温等离子体的电子温度与磁场时,在阻带内会产生一尖锐的透射峰.这种现象在冷等离子体模型中从来没有出现过.本文主要对电子温度和外加磁场两个影响因素进行讨论.研究发现,禁带内出现的透射峰频率受磁场影响,而峰值幅度受温度影响.计算得到了不同外加磁场条件下产生高透过率(透射率约为1)时的电子温度.基于该结果进一步研究了透射峰出现的规律,并通过曲线拟合的方法得到了透射峰频率所遵循的计算公式.数值结果表明透射峰频率与外磁场之间为正比例函数关系,而峰值电子温度取值与外磁场的关系表现为指数规律.最后对拟合得到的方程采用时域有限差分法进行了验证,数值结果与解析解符合较好,证明了该研究的正确性.
In the hypersonic flight, the air surrounding an aircraft under the effect of high temperature will be ionized. The ionized gas is called plasma. Because of the influence of interaction between electromagnetic wave, in some cases the communication will be interrupted. High temperature effect is an important characteristic of the plasma. Therefore, the study of terahertz wave propagation in high temperature plasma is of great significance. In this paper, the transmission of terahertz wave in a high temperature plasma slab is studied. Generally, high temperature plasma is an anisotropic medium. The electromagnetic wave propagates in anisotropic high-temperature plasma and forms left-hand circular polarization mode or right-hand circular polarization(RCP) mode. It is found that the RCP wave can exhibit some novel characteristics, such as the forbidden band transmission characteristics, which is discovered in this paper. The transmission characteristics of terahertz wave in high temperature plasma are studied analytically. The results show that when the frequency of terahertz wave is lower than plasma frequency, the wave cannot be propagated in high temperature plasma, and it shows a stopband characteristic. When the frequency is higher, it can be transmitted through the plasma,and it presents a passband characteristic. These are consistent with the propagation characteristics of electromagnetic waves in cold plasma. However, some characteristics in high temperature plasma are different from those in the cold plasma. In high temperature plasma, the transmission characteristics are influenced by the electron temperature and external magnetic field. When the two parameters are chosen appropriately, a sharp transmission peak will be produced in the stopband. This phenomenon has never been found in cold plasma models before. And the paper will discuss this problem by the two influencing factors. It is also found that the frequency of the transmission peak is affected by magnetic field, and the peak amplitude is influenced by electron temperature. The electron temperatures at high transmittance(transmittance is about 1) under different applied magnetic fields are calculated. In order to study the law embodied in the data, the method of data fitting is adopted. And the formula of transmission peak frequency is obtained by curve fitting. The fitting results show that the transmission peak frequency is proportional to the external magnetic field. The relationship between peak electron temperature and external magnetic field is exponential. Finally,the fitting formula is verified by the finite-difference time-domain method. The numerical results are in good agreement with the analytical solution results, which proves the correctness of the work.
In the hypersonic flight, the air surrounding an aircraft under the effect of high temperature will be ionized. The ionized gas is called plasma. Because of the influence of interaction between electromagnetic wave, in some cases the communication will be interrupted. High temperature effect is an important characteristic of the plasma. Therefore, the study of terahertz wave propagation in high temperature plasma is of great significance. In this paper, the transmission of terahertz wave in a high temperature plasma slab is studied. Generally, high temperature plasma is an anisotropic medium. The electromagnetic wave propagates in anisotropic high-temperature plasma and forms left-hand circular polarization mode or right-hand circular polarization(RCP) mode. It is found that the RCP wave can exhibit some novel characteristics, such as the forbidden band transmission characteristics, which is discovered in this paper. The transmission characteristics of terahertz wave in high temperature plasma are studied analytically. The results show that when the frequency of terahertz wave is lower than plasma frequency, the wave cannot be propagated in high temperature plasma, and it shows a stopband characteristic. When the frequency is higher, it can be transmitted through the plasma,and it presents a passband characteristic. These are consistent with the propagation characteristics of electromagnetic waves in cold plasma. However, some characteristics in high temperature plasma are different from those in the cold plasma. In high temperature plasma, the transmission characteristics are influenced by the electron temperature and external magnetic field. When the two parameters are chosen appropriately, a sharp transmission peak will be produced in the stopband. This phenomenon has never been found in cold plasma models before. And the paper will discuss this problem by the two influencing factors. It is also found that the frequency of the transmission peak is affected by magnetic field, and the peak amplitude is influenced by electron temperature. The electron temperatures at high transmittance(transmittance is about 1) under different applied magnetic fields are calculated. In order to study the law embodied in the data, the method of data fitting is adopted. And the formula of transmission peak frequency is obtained by curve fitting. The fitting results show that the transmission peak frequency is proportional to the external magnetic field. The relationship between peak electron temperature and external magnetic field is exponential. Finally,the fitting formula is verified by the finite-difference time-domain method. The numerical results are in good agreement with the analytical solution results, which proves the correctness of the work.
引文
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[22]Tian Y,Han Y P,Ling Y J,Ai X 2014 Phys.Plasmas21 1768
[2]Chen W,Guo L X,Li J T,Dan L 2017 Acta Phys.Sin.66 084102(in Chinese)[陈伟,郭立新,李江挺,淡荔2017物理学报66 084102]
[3]Tian Y,Ai X,Han Y P,Guo L X 2015 Phys.Plasmas22 290
[4]Guo L J,Guo L X,Li J T 2017 Phys.Plasmas 24 022108
[5]Gu L,Tan Z Y,Cao J C 2013 Phys.42 695(in Chinese)[顾立,谭智勇,曹俊诚2013物理42 695]
[6]Hu Q L,Liu S B,Li W 2008 Chin.Phys.B 17 1050
[7]Zhou W,Ji K,Chen H M 2017 Acta Phys.Sin.66054210(in Chinese)[周雯,季珂,陈鹤鸣2017物理学报66 054210]
[8]Chen C M,Bai Y L,Zhang J,Yang Y,Wang J 2018High Power Laser and Particle Beams 30 013101(in Chinese)[陈春梅,摆玉龙,张洁,杨阳,王娟2018强激光与粒子束30 013101]
[9]Yuan C X,Zhou Z X,Xiang X L,Sun H G,Wang H,Xing M D,Luo Z J 2011 Nucl.Instrum.Meth.B 26923
[10]Yuan C X,Zhou Z X,Zhang J W W,Xiang X L,Yue F,Sun H G 2011 IEEE Trans.Plasma Sci.39 1577
[11]Wu X G,Hu Y,Wang P,Nan L 2018 High Power Laser and Particle Beams 30 043102(in Chinese)[伍习光,胡洋,王平,南琳2018强激光与粒子束30 043102]
[12]Liu J X,Zhang J L,Su M M 2014 Acta Phys.Sin.63137501(in Chinese)[刘建晓,张郡亮,苏明敏2014物理学报63 137501]
[13]Liu J X,Su M M,You X,Li A P,Yang H W 2013 Sci.Tech.Eng.13 4418(in Chinese)[刘建晓,苏明敏,游雄,李爱萍,杨宏伟2013科学技术与工程13 4418]
[14]Yang H W,Zhang Y,Chen R S 2007 J.Nanjing University of Science and Technology 31 491(in Chinese)[杨宏伟,张云,陈如山2007南京理工大学学报31 491]
[15]Song W,Zhang H 2016 J.Electromagnet Wave 30 1321
[16]Rahmani Z,Moradi H 2018 Optik 155 81
[17]Yang H W 2012 J.Russ Laser Res.33 356
[18]Lee J H,Kalluri D K 1999 IEEE Trans.Antennas Propag.47 1146
[19]Jazi B,Rahmani Z,Shokri B 2013 IEEE Trans.Plasma Sci.41 290
[20]Xie C F,Rao K J 1999 Electromagnetic Field and Wave(3rd Ed.)(Beijing:Higher Education Press)pp237-239(in Chinese)[谢处方,饶克谨1999电磁场与电磁波(第3版)(北京:高等教育出版社)第237-239页]
[21]Platzman P M,Buchsbaum S J 1963 Phys.Rev.132 1
[22]Tian Y,Han Y P,Ling Y J,Ai X 2014 Phys.Plasmas21 1768