Propagation Characteristics of Obliquely Incident Terahertz Waves in High-Temperature Magnetized Plasma

Author(s):  
Xiao-Huan Wan ◽  
Zhi-Kun Zhou ◽  
Juan Zhang ◽  
Xue-Ping Ren ◽  
Yu-Shan Zhou ◽  
...  
2021 ◽  
Vol 134 (2) ◽  
pp. 24002
Author(s):  
Xiao-Huan Wan ◽  
Zhi-Kun Zhou ◽  
Juan Zhang ◽  
Xiao-Lin Li ◽  
Xue-Ping Ren ◽  
...  

AIP Advances ◽  
2017 ◽  
Vol 7 (12) ◽  
pp. 125325 ◽  
Author(s):  
Yunxian Tian ◽  
Weizhong Yan ◽  
Xiaoliang Gu ◽  
Xiaolin Jin ◽  
Jianqing Li ◽  
...  

Most of the matter in the Universe is in the plasma state. A plasma will be defined and the concepts of quasi-neutrality and Debye distance introduced. The subject has its historical roots in gas discharge, astrophysics and ionospheric physics. Key theoretical concepts were developed in the context of those subjects. However, only in the last two decades, under the pressures of the controlled thermonuclear and space exploration programmes, have these concepts been tested experimentally. The theory of collisions in plasma has special features owing to the Coulomb nature of the interaction. Magnetized plasma is a medium in which a rich variety of small signal waves can propagate. Charged particle—wave interactions lead to collisionless (Landau) damping and growth mechanisms. Finally, nonlinear phenomena in plasma can and do change its transport properties by orders of magnitude. Our lack of detailed understanding of these nonlinear phenomena applies equally to natural plasmas and to plasmas in both inertially and magnetically confined fusion systems. This feature provides the challenge and the fascination of high temperature plasma physics.


2004 ◽  
Vol 11 (5/6) ◽  
pp. 647-657 ◽  
Author(s):  
R. A. Treumann ◽  
C. H. Jaroschek ◽  
O. D. Constantinescu ◽  
R. Nakamura ◽  
O. A. Pokhotelov ◽  
...  

Abstract. Mirror mode turbulence is the lowest frequency perpendicular magnetic excitation in magnetized plasma proposed already about half a century ago by Rudakov and Sagdeev (1958) and Chandrasekhar et al. (1958) from fluid theory. Its experimental verification required a relatively long time. It was early recognized that mirror modes for being excited require a transverse pressure (or temperature) anisotropy. In principle mirror modes are some version of slow mode waves. Fluid theory, however, does not give a correct physical picture of the mirror mode. The linear infinitesimally small amplitude physics is described correctly only by including the full kinetic theory and is modified by existing spatial gradients of the plasma parameters which attribute a small finite frequency to the mode. In addition, the mode is propagating only very slowly in plasma such that convective transport is the main cause of flow in it. As the lowest frequency mode it can be expected that mirror modes serve as one of the dominant energy inputs into plasma. This is however true only when the mode grows to large amplitude leaving the linear stage. At such low frequencies, on the other hand, quasilinear theory does not apply as a valid saturation mechanism. Probably the dominant processes are related to the generation of gradients in the plasma which serve as the cause of drift modes thus transferring energy to shorter wavelength propagating waves of higher nonzero frequency. This kind of theory has not yet been developed as it has not yet been understood why mirror modes in spite of their slow growth rate usually are of very large amplitudes indeed of the order of |B/B0|2~O(1). It is thus highly reasonable to assume that mirror modes are instrumental for the development of stationary turbulence in high temperature plasma. Moreover, since the magnetic field in mirror turbulence forms extended though slightly oblique magnetic bottles, low parallel energy particles can be trapped in mirror modes and redistribute energy (cf. for instance, Chisham et al. 1998). Such trapped electrons excite banded whistler wave emission known under the name of lion roars and indicating that the mirror modes contain a trapped particle component while leading to the splitting of particle distributions (see Baumjohann et al., 1999) into trapped and passing particles. The most amazing fact about mirror modes is, however, that they evolve in the practically fully collisionless regime of high temperature plasma where it is on thermodynamic reasons entirely impossible to expel any magnetic field from the plasma. The fact that magnetic fields are indeed locally extracted makes mirror modes similar to "superconducting" structures in matter as known only at extremely low temperatures. Of course, microscopic quantum effects do not play a role in mirror modes. However, it seems that all mirror structures have typical scales of the order of the ion inertial length which implies that mirrors evolve in a regime where the transverse ion and electron motions decouple. In this case the Hall kinetics comes into play. We estimate that in the marginally stationary nonlinear state of the evolution of mirror modes the modes become stretched along the magnetic field with k||=0 and that a small number the order of a few percent of the particle density is responsible only for the screening of the field from the interior of the mirror bubbles.


2010 ◽  
Vol 3 (4) ◽  
pp. 042701 ◽  
Author(s):  
Ryosuke Kaneko ◽  
Iwao Kawayama ◽  
Hironaru Murakami ◽  
Masayoshi Tonouchi

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