外加磁场微波等离子推力器内流场数值模拟

为了提高微波等离子推力器性能，改善等离子体对电磁波能量的吸收状况，提高核心区温度，提出外加磁场的方案，并对热等离子体进行了数值模拟.假设局域热平衡条件，采用Navier-Stokes，Maxwell和Saha方程，利用压力修正的半隐格式和时域有限差分求解方法，建立了径向磁镜场下推力器内等离子体流场的数值计算模型.数值模拟结果表明：外加磁场后的磁感应强度小于0.5 T时，推力器内热等离子体核心区最高温度随磁感应强度的增加而迅速提高.外加磁场后的磁感应强度大于0.5 T时，核心区最高温度随磁感应强度的增加而缓慢提高.磁感应强度为0.5 T时，热等离子体核心区最高温度与不加磁场相比提高了24%.外加磁场对等离子体流场速度分布影响不大. 关键词： 等离子体模拟 等离子体相互作用 等离子体流动     

Plane Waves Propagating in Chiral Plasma and Chiral Ferrite Media

Plane wave propagation in chiral plasma and chiral ferrite media is studied in kDB coordinate system. General wave equations and characteristic equations of plane waves propagating along an arbitrary direction in chiral plasma and in chiral ferrites are derived in simple formulations respectively. Four wavenumbers and their corresponding dispersion characteristics are resulted for propagation both along and normal to the biasing magnetic field. When plane wave with negative helicity propagates along the biasing magnetic field in chiral ferrites, backward waves emerge. However backward waves occur with both positive and negative helicities when propagating along the biasing magnetic field in chiral plasma.     

多光子非线性Compton散射对等离子体中电子运动的影响

应用多光子非线性Compton散射模型,研究了多光子非线性Compton散射对激光等离子体中电子运动的影响,提出了将入射激光和Compton散射光形成的耦合光、耦合光与等离子体产生的自生磁场形成的混合场作为加速电子的新机制,对电子动量和能量方程进行了修正和数值模拟。结果表明,当混合场的电场振幅与磁场振幅相等时,回旋共振电子在与混合场作用时间内能被加速到很高的能量;电子加速能量随耦合光幅值的增大而增大,随电子耦合初始角度的增大而周期变小,随电子横向耦合归一化初始速度的增大,开始时较快增加,之后缓慢增加,最后趋于稳定。     

Beat Heating of Collisional and Magnetised Plasma

The heating of a plasma by stimulating plasma electrons as well as plasma ions with two anti-parallel electromagnetic waves under the influence of a uniform static magnetic field is studied using Maxwell's equations and equations of motion. A formula for the power absorption per unit volume of the plasma is derived and effects of collisions and magnitude and orientation of the magnetic field on the beat heating are examined numerically. It is observed that the average power absorption in the absence of ion-neutral collisions in the plasma barely exceeds unity in the units of pure Langmuir mode excitation where as in the presence of ion-neutral collisions the power absorption immediately shoots up to a very high value.     

Self-Focusing and de-Focusing of Intense Left- and Right-Hand Polarized Laser Pulse in Hot Magnetized Plasma in the Presence of an External Non-Uniform Magnetized Field

In this paper, self-focusing of an intense circularly polarized laser beam in the presence of a non-uniform positive guide magnetic field with slope constant parameter δ in hot magnetized plasma, using Maxwell’s equations and relativistic fluid momentum equation is investigated. An envelope equation governing the spot-size of laser beam for both of left- and right-hand polarizations has been derived, and the effects of the plasma temperature and magnetic field on the electron density distribution of hot plasma with respect to variation of normalized laser spot-size has been studied. Numerical results show that self-focusing is better increased in the presence of an external non-uniform magnetic field. Moreover, in plasma density profile, self-focusing of the laser pulse improves in comparison with no non-uniform magnetic field. Also, with increasing slope of constant parameter of the non-uniform magnetic field, the self-focusing increases, and subsequently, the spot-size of laser pulse propagated through the hot magnetized plasma decreases.     

Dielectric tensor elements for the description of waves in rotating inhomogeneous magnetized plasma spheroids

The dielectric permittivity tensor elements of a rotating cold collisionless plasma spheroid in an external magnetic field with toroidal and axial components are obtained. The effects of inhomogeneity in the densities of charged particles and the initial toroidal velocity on the dielectric permittivity tensor and field equations are investigated. The field components in terms of their toroidal components are calculated and it is shown that the toroidal components of the electric and magnetic fields are coupled by two differential equations. The influence of thermal and collisional effects on the dielectric tensor and field equations in the rotating plasma spheroid are also investigated. In the limiting spherical case, the dielectric tensor of a stationary magnetized collisionless cold plasma sphere is presented.     

Condensation Instability in Partially Ionized Plasma in a Magnetic Field

The occurrence conditions of the condensation instability in heat-releasing partially ionized plasma in an external magnetic field with an induction vector normal to the direction along which a perturbation occurs are considered. Linear equations describing isobaric perturbation dynamics in the two-liquid plasma model are derived. Using these equations, a dispersion relation for condensation modes is derived and their time increments are calculated for various degrees of plasma ionization and magnetic fields.     

Rossby waves in the magnetic fluid dynamics of a rotating plasma in the shallow-water approximation

We have studied rotating magnetohydrodynamic flows of a thin layer of astrophysical plasma with a free boundary in the β-plane. Nonlinear interactions of the Rossby waves have been analyzed in the shallow-water approximation based on the averaging of the initial equations of the magnetic fluid dynamics of the plasma over the depth. The shallow-water magnetohydrodynamic equations have been generalized to the case of a plasma layer in an external vertical magnetic field. We have considered two types of the flow, viz., the flow in an external vertical magnetic field and the flow in the presence of a horizontal magnetic field. Qualitative analysis of the dispersion curves shows the presence of three-wave nonlinear interactions of the magnetic Rossby waves in both cases. In the particular case of zero external magnetic field, the wave dynamics in the layer of a plasma is analogous to the wave dynamics in a neutral fluid. The asymptotic method of multiscale expansions has been used for deriving the nonlinear equations of interaction in an external vertical magnetic field for slowly varying amplitudes, which describe three-wave interactions in a vertical external magnetic field as well as three-wave interactions of waves in a horizontal magnetic field. It is shown that decay instabilities and parametric wave amplification mechanisms exist in each case under investigation. The instability increments and the parametric gain coefficients have been determined for the relevant processes.     

等离子体在高频调制场作用下形成自生磁场的机制

研究了等离子体在高频调制场作用下,形成自生磁场的机制.通过求解双时标双流体方程,可以得到一组相互耦合的非线性方程。这组方程可以用来描述自生磁场的形成和演化.数值计算的结果显示,在高频调制场作用下,可以有自生磁场形成.计算得到的磁场强度和特征长度,与太阳日冕内的观测值符合得很好.随着时间的增加,自生磁场可以产生塌缩现象,导致磁场强度在很小的范围内有很大的值. 关键词： 自生磁场 双流体方程 高频调制场     

Ionization formation of plasma inhomogeneity by the near-zone field of a magnetic-type source in a magnetized plasma

An investigations is made of the steady-state structure of a plasma inhomogeneity arising as a result of high-frequency heating and additional ionization of a background magnetized plasma by the near-zone field of a magnetic-type source (ring electric current). It is assumed that the source axis is parallel to an external magnetic field; the source frequency belongs in the low hybrid band. The main attention is focused on the particular case (important for possible applications) when the characteristic longitudinal and transverse scales of density distribution considerably exceed the corresponding scales of distribution of the electron temperature and of the source field. Simplified equations for the near-zone field of the source, the electron temperature, and the plasma density are written for this particular case. Based on the numerical solution of these equations, steady-state distributions of plasma parameters in the formed plasma inhomogeneity are found. It is demonstrated that a plasma inhomogeneity proves to be markedly extended along the external magnetic field. It is found that, for the values of the source current that are attainable under the conditions of active ionospheric and model laboratory experiments, the maximum plasma density in a nonuniform plasma may appreciably exceed the background value.     

磁化等离子体填充螺旋线的色散方程

利用等离子体流体理论和纵向场分量法，结合螺旋线的导电面模型，对在有限磁场作用下，填充等离子体的螺旋线进行了严格的场分析. 在给出各区域电磁场分量表达式的基础上，利用螺旋线的边界条件，导出了磁化等离子体填充螺旋线中电磁波传播所满足的色散方程，并对所导出的色散方程进行了讨论. 关键词： 有限磁场 等离子体 螺旋线 色散方程     

Enhancement of electron density in the interaction of high-power electromagnetic waves with inhomogeneous magnetized plasma

Propagation characteristics of a high-power electromagnetic wave through an inhomogeneous magnetized plasma is investigated. Considering the momentum transfer equations for electrons and ions and taking into account the ponderomotive force, the distribution of electron density and dielectric permittivity are obtained. Using non-linear dielectric permittivity and Maxwell's equations in the absence of external current and charge densities, non-linear wave equations are achieved. The results indicate that the external static magnetic field can modify the profiles of both the electric and magnetic fields. It is also shown that the external static magnetic field enhances the amplitude of the electron density and the non-linear dielectric permittivity.     

等离子体的热力学研究

本文利用不可逆过程热力学讨论了在均匀磁场作用下的等离子体,得到了电流方程并指出了磁场对电流的影响。同时讨论了部分游离的等离子体中的电流、扩散和热扩散对电流的影响以及磁场对扩散的影响。     

Initial-value problem for plasma oscillations in a uniform magnetic field

The solution is given of the initial-value problem for the nonrelativistic linearised Vlasov-Maxwell equations describing longitudinal and transverse plasma oscillations in an external uniform magnetic field. The problem is solved for all directions of propagation except normal to the external magnetic field, and the equilibrium distribution is not assumed isotropic. The method of solution is an extension of Van Kampen's eigenfunction expansion technique, already developed considerably by Zelazny and McCure, in which the problem is reduced to the solution of a system of singular integral equations.     

等离子体在磁场中能级分离可能产生的影响

考虑到磁场中的带电粒子在与磁场方向垂直的两个方向上的能级分离，采用玻耳兹曼统计分布，得到几个公式.说明了低温强磁场时可能出现的情况.据此说明了如何对磁流体方程给予一定的修正. 关键词：     

Propagation of electron cyclotron waves in a weakly relativistic plasma with steep density and temperature profiles

Summary A detailed analysis is made of the deduction of systems of differential equations describing the propagation of both ordinary and extraordinary waves in the electron cyclotron frequency range in a stratified plasma, perpendicularly to the magnetic field and across the electroncyclotron fundamental resonance layer. The equations are derived under conditions of not too large electron temperature (the so-called weakly relativistic condition) and of very weak nonuniformities of the confining magnetic field. The effects of the nonhomogeneities of the equilibrium plasma density and temperature are carefully examined. It is shown that the propagation equations derived previously in the literature can be extended with only a moderately larger effort in computations to take account also of very strong density and temperature gradients.     

Numerical Analysis of Symmetrical Waves Dispersion in a Nonisothermal Plasma Waveguide in a Magnetic Field

Dispersion equations of a nonisothermal plasma waveguide in a constant external magnetic field are derived, when the magnetic field intensity tends to infinity. The plasma electrons' thermal velocity are taken in mind. A numerical analysis of dispersion equations for the E- (TH-) and H- (TE-) waves is made. In the high-frequency range it shows the possibility of the slow E-waves exciting with a higher frequency than the electron Langmuir frequency. In the range near to the ion Langmuir frequency it shows the existence of waves with an anomalous dispersion. These waves are named low-frequency backward E-waves and it is shown, that in some frequency ranges they change the group velocity sign. The dispersion is investigated also in respect to the waveguide plasma filling.     

Laser-Plasma Interaction in Presence of an Obliquely External Magnetic Field: Application to Laser Fusion without Radioactivity

In this paper, the nonlinear interaction of ultra-high power laser beam with fusion plasma at relativistic regime in the presence of obliquely external magnetic field has been studied. Imposing an external magnetic field on plasma can modify the density profile of the plasma so that the thermal conductivity of electrons reduces which is considered to be the decrease of the threshold energy for ignition. To achieve the fusion of Hydrogen-Boron (HB) fuel, the block acceleration model of plasma is employed. Energy production by HB isotopes can be of interest, since its reaction does not generate radioactive tritium. By using the inhibit factor in the block model acceleration of plasma and Maxwell's as well as the momentum transfer equations, the electron density distribution and dielectric permittivity of the plasma medium are obtained. Numerical results indicate that with increasing the intensity of the external magnetic field, the oscillation of the laser magnetic field decreases, while the dielectric permittivity increases. Moreover, the amplitude of the electron density becomes highly peaked and the plasma electrons are strongly bunched with increasing the intensity of external magnetic field. Therefore, the magnetized plasma can act as a positive focusing lens to enhance the fusion process. Besides, we find that with increasing θ-angle (from oblique external magnetic field) between 0 and 90°, the dielectric permittivity increases, while for θ between 90° and 180°, the dielectric permittivity decreases with increasing θ.     

Gluon transport equations,plasma oscillations,and screening

The gluon transport equations (Phys. Lett. 177B (1986) 402) are reconsidered to derive a consistent semiclassical limit. Introducing the color current of gluon fluctuations around a classical mean field, we calculate the color permeability function of a collisionless gluon plasma in linear response approximation. The dispersion relations and electric screening length agree with one-loop high temperature QCD results. We find no magnetic screening atO(g ²) and predict transverse magnetic plasma oscillations similar to electric ones. The extension to include particle production by a mean color field is shortly described.     

Concerning microsecond megaampere-current plasma opening switches

The operation mechanism of a microsecond megaampere-current plasma opening switch is considered. The magnetic field penetrates into the plasma via near-electrode diffusion. The increase in the degree of plasma magnetization due to electron heating results in an increase in plasma resistivity and current break. The problem of calculating a plasma opening switch is mathematically formulated. The problem reduces to simultaneously solving one-fluid two-temperature MHD equations with allowance for the Hall current and two-dimensional electric circuit equations. To analyze the solution obtained, one-dimensional equations are derived based on the assumption that the size of the electrode region in which the plasma is strongly magnetized is much smaller that the plasma column length. In this approximation, the operating modes of a plasma opening switch are studied numerically. On long time scales (≥2–3 μs), the operation is limited by plasma ejection from the interelectrode gap. On short time scales (≤1 μs), the dominant process is the penetration of the magnetic field with the current velocity. The results of the calculations are compared with the available experimental data. The developed concept and numerical procedure are used to optimize the scheme for an explosion experiment on breaking megaampere currents under conditions similar to those in the EMIR complex.