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EM-Radiation of Anisotropic Plasma (R)

#0310


Theoretical Study of Generation of the Electromagnetic Radiation from a Plasma with Anisotropic Electron Velocity Distribution.

Tech Area / Field

  • PHY-PLS/Plasma Physics/Physics

Status
8 Project completed

Registration date
13.12.1994

Completion date
28.08.2000

Senior Project Manager
Ryabeva E V

Leading Institute
VNIIEF, Russia, N. Novgorod reg., Sarov

Supporting institutes

  • FIAN Lebedev, Russia, Moscow

Collaborators

  • US Department Army/US Army Space and Strategic Defense Command / Missile Defense and Space Technology Center (MDSTC), USA, AL, Huntsville\nLos-Alamos National Laboratory, USA, NM, Los-Alamos\nLawrence Livermore National Laboratory, USA, CA, Livermore

Project summary

The objective of this project is to develop a better understanding of the dynamic and transport properties of plasmas with anisotropic electron distribution and provide a theoretical background for new methods of nonequiliblium plasma diagnostics. It involves an extensive computer modeling and a development of corresponding analytical theory. A plasma with anisotropic electron energy distribution can be easily found in many laboratory devices and in natural environment. A number of different physical processes might be responsible for that. An anisotropic electron distribution has been predicted and observed in the laboratory experiments with plasmas produced by a ultrashort laser pulse. A fast compression of magnetized plasma is also resulted in anisotropy of the electron pressure. In natural astrophysical and geophysical environments and also in active experiments in an outer space an anisotropy of plasma pressure might be produced with a powerful pulse of x-ray radiation. In collisional plasmas the free energy of anisotropic electrons is dissipated fast, however, in high temperature weakly collisional plasmas it may be a source of instability and because of that a part of free energy may be transformed into quasistatic, large scale electromagnetic fluctuations and result in an electromagnetic emission. Therefore, an anisotropic plasma can be considered as a source of electromagnetic radiation or this emission can be used for the remote monitoring of plasma parameters.

Electromagnetic wave generation is a result of Weibel-type instability of an anisotropic particle distribution. These fields are quasistatic (have frequency much less than the electron plasma frequency) and large scale (comparable or larger than the electron skin depth) and therefore may significantly affect plasma opacity and transport characteristics. In spite of the fact that computations of the nonlinear stage of Weibel instability has been started more than 25 years ago, a little progress has been made until recently this problem has been attacked once more in virtue of advanced computer simulations and novel analytical methods. This is motivated by the fast ignitor concept in laser fusion, research in laser-particle accelerators and laser pumped x-ray lasers in view of recent discovery of subpicosecond laser pulses and astrophysical applications.

The group of applicants have started the work on nonlinear theory of Weibel-like instabilities and emission from anisotropic plasmas several years ago, and some results have already been obtained. A new quasihydrodynamical model for electrons with anisotropic temperature has been proposed and tested against the full kinetic treatment and particle-in-sell simulations [1, 2]. It is shown in [3] that under special requirements a significant part of the anisotropy energy can be transferred into electromagnetic field and may propagate as a whistler mode in a plasma. Recently the transport theory has been advanced for the conditions of semicollisional plasma when the electron mean free path is compared to the plasma inhomogeneity scale length [4]. These conditions are appropriate for electron anisotropy formation and excitation of the Weibel instability. However the possible influence of large scale, low frequency electromagnetic fields on the plasma transport properties has not been addresses yet.

The present project is thought as a combined attack on the nonlinear theory of anisotropic plasmas based on the analytical approach and kinetic and hydrodynamic computer simulations. The FIAN's part of the research team will contribute to the analytical theory and simulations based on anisotropic electron hydrodynamics and to the theory of nonlocal electron transport. The VNIIEF's part has a unique expertise in computer modeling and will develop a kinetic code for semicolliisonal plasmas. The project will address the problems of: (i) characterization of anisotropic plasmas produced with different energy sources, (ii) the development and nonlinear saturation of the Weibel-type plasma instabilities, (iii) formation of nonlinear vortical plasma structures and their stability, (iv) effect of quasistatic electromagnetic on the transport properties of a plasma, and (v) assessment the conditions for effective emission of electromagnetic fields from a plasma into outer space and optimization of the radiation energy. The results of the project will be published in scientific journals and will contribute to the theory of turbulent and nonequilibrium plasmas. In virtue of the theory and computer simulations we will address practical problems: (i) monitoring of the anisotropic plasma characteristics from its electromagnetic emission, (ii) effect of laser induced anisotropy on performance of laser fusion targets, laser-particle accelerators, and x-ray lasers, (iii) design of efficient converter of a hard x-ray and powerful optical radiation into a microwave emission, (iv) x -ray spectroscopy of anisotropic plasmas. Among these applications we consider a plasma diagnostics via its electromagnetic emission as most important one. If the project succeeded, it will allow a microwave and x-ray monitoring of remote plasma objects and may also provide some valuable information about the characteristics of the source of anisotropy. The subject of this project correlates with activities of European and North American scientists studying the nonlinear dynamics of anisotropic plasmas. We already carry out the collaboration with the University of Alberta (Edmonton, Canada) and INRS-Energie (University of Montreal, Varennes, Canada) on the theory of nonlocal transport, laser-induced plasma anisotropy, and nonlinear wave propagation in inhomogeneous plasmas. We also plan no establish international contacts during the period of this project with the Laboratory for Utilization of Intense Lasers (LULI, Ecole Polytechnique, France), the University of California, Los Angeles, and Lawrence Livermore National Laboratory.


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