Heating of astrophysical plasma due to rotation

It is shown that low-frequency transverse MHD waves may undergo damping inside a rotating stellar body. It is suggested that rotation may affect the heating of the stellar interior.The author is grateful to Dr. B. Chakraborty and B. Basu, Dept. of Math., Jadavpur University, for their guidance in the preparation of this paper.     

Ion acoustic soliton propagation in a magnetized relativistic plasma

Summary The Korteweg-de Vries equation for ion acoustic waves in the presence of weakly relativistic ion streaming velocity is derived in a magnetic plasma. It is found that relativistic effects are important in the solitary wave propagation for both fast and slow modes. Earlier results are reconfirmed. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Ion cyclotron electrostatic waves in a low-temeprature low-density magnetized plasma

Summary The electrostatic dispersion relation for a low-temperature, low-density magnetized plasma has been studied in the range of the ion cyclotron frequency and its first harmonics. The presence of a forward wave and of an infinite number of backward waves has been shown. The characteristics of propagation of these modes and the possibility of conversion are analysed.

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Riassunto Viene studiata la relazione di dispersione elettrostatica relativa ad un plasma magnetizzato di bassa densità e di bassa temperatura nel campo della frequenza ciclotronica ionica e delle sue prime armoniche. Si mostra la presenza di un unico modo forward e di un insieme infinito di modi backward. Si analizzano le caratteristiche di propagazione di queste onde e la possibilità di conversioni tra di esse.

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Резюме Исследуется электростатическое дисперсионное соотношение для намагниченной плазмы с низкой температурой и низкой плотностью в области ионной циклотронной частоты и ее первой гармоники. Показывается наличие единственной моды в направлении вперед и бесконечного числа волн в обратном направлении. Анализируются характеристики распространения этих мод и возможность конверсии.

     

Modulation of waves due to charge-exchange collisions in magnetized partially ionized space plasma

A nonlinear time dependent fluid simulation model is developed that describes the evolution of magnetohydrodynamic waves in the presence of collisional and charge exchange interactions of a partially ionized plasma. The partially ionized plasma consists of electrons, ions and a significant number of neutral atoms. In our model, the electrons and ions are described by a single fluid compressible magnetohydrodynamic (MHD) model and are coupled self-consistently to the neutral gas, described by the compressible hydrodynamic equations. Both the plasma and neutral fluids are treated with different energy equations that describe thermal energy exchange processes between them. Based on our self-consistent model, we find that propagating Alfvénic and fast/slow modes grow and damp alternately through a nonlinear modulation process. The modulation appears to be robust and survives strong damping by the neutral component.     

Generation of sheath in magnetized plasma under the impact of slow rotation

In this study, we have tried to investigate the generation of sheath in magnetized plasma rotating with a uniform angular velocity about an axis making an angle with the direction of plasma-acoustic wave propagation. In a marked contrast to the earlier studies, here the simultaneous impact of slow rotation and external magnetic field has been taken into consideration. Previous studies have revealed that the Coriolis force generated from rotation has a tendency to produce an equivalent magnetic field effect as and when the ionized medium rotates. The variations of sheath potential with normalized distance for different values of angles of rotation as well as for different values of Mach number have also been investigated for typical plasma parameters.     

Experimental observation of intermittent route to chaos in magnetized filamentary discharge plasma due to the cylindrical plasma bubble

We delineate an experimental observation of the effect of the magnetic field along with mesh grid biasing in the presence of a cylindrical plasma bubble in a filamentary discharge magnetised plasma system. The cylindrical mesh grid of 80% optical transparency has been negatively biased and introduced in the plasma for creating a plasma bubble. Plasma floating potential fluctuations have been taken outside (LP1) and inside (LP2) of the plasma bubble. It has been noticed that as the external magnetic field is increased the oscillation pattern shows intermittent route to chaos as the system evolved from regular type of relaxation oscillations (of larger amplitude) to an irregular type of oscillations (of smaller amplitude) We have used recurrence quantification analysis (RQA) to the observed intermittency to chaos in the plasma. The main measures of RQA are laminarity (LAM) and determinism (DET). The laminarity measure can be associated with the average time between the chaotic burst in the intermittency. It has also been observed that the DET depends on the control parameter and decreases exponentially, features like a dip in skewness and a hump in the kurtosis with the variation of control parameter have been noticed, which are the strong evidence of intermittent behaviour of the system. Further, a numerical model has been developed to the observed experimental analysis of the intermittent route to chaos.     

非对心碰撞与旋转问题

讨论了两小球的非对心碰撞,对碰撞后两小球的旋转问题做了详细的讨论,并给出了计算结果,引入了碰撞角和碰撞临界角的概念。     

Spontaneous Faraday rotation due to strong laser radiation in a plasma

Theoretical studies on intense laser radiation interacting with plasma reveal an induced nonlinear birefringence which turns out to be spontaneous Faraday rotation. Here, this rotation is called nonlinear Faraday rotation (NFR). The expressions for the nonlinear refractive indices of the laser fields are calculated both in relativistic and non-relativistic limits for a two-component plasma. The NFR angles due to nonlinear induced birefringence are derived in the absence of externally imposed magnetic fields. It is shown that, in the relativistic limit, the electron motion plays an important role in producing NFR and so in the generation of induced magnetic fields.     

脉冲驱动磁化等离子体内爆升温点火的数值模拟北大核心CSCD

通过建立物理模型,用一维三温拉氏磁流体力学程序分析了由强电流(MA)脉冲驱动的金属套筒内爆压缩磁化等离子体的升温点火及能量增益过程。分析了脉冲驱动的金属套筒内爆、不同驱动源对金属套筒内爆升温的影响、Z箍缩过程中内嵌磁场和预加热温度对磁化等离子体升温的影响,以及点火需要的初态参数和点火后的能量输出。此外,对该过程中磁场增加α粒子能量沉积、降低电子离子热传导能量损失的物理机制做了介绍和分析。磁流体数值模拟结果显示:当初始的内嵌磁场和燃料的预加热温度分别取5T和250eV时,即可获得超过4keV的升温,初始参数包括内嵌磁场、预加热温度、燃料密度、套筒尺度、驱动脉冲幅值、加载时间等。在一定的条件下,点火成功,可产生kT量级的强磁场,并获得百kJ/mm量级的能量输出。     

脉冲驱动磁化等离子体内爆升温点火的数值模拟

通过建立物理模型,用一维三温拉氏磁流体力学程序分析了由强电流（MA）脉冲驱动的金属套筒内爆压缩磁化等离子体的升温点火及能量增益过程。分析了脉冲驱动的金属套筒内爆、不同驱动源对金属套筒内爆升温的影响、Z箍缩过程中内嵌磁场和预加热温度对磁化等离子体升温的影响,以及点火需要的初态参数和点火后的能量输出。此外,对该过程中磁场增加粒子能量沉积、降低电子离子热传导能量损失的物理机制做了介绍和分析。磁流体数值模拟结果显示：当初始的内嵌磁场和燃料的预加热温度分别取5 T和250 eV时,即可获得超过4 keV的升温,初始参数包括内嵌磁场、预加热温度、燃料密度、套筒尺度、驱动脉冲幅值、加载时间等。在一定的条件下,点火成功,可产生kT量级的强磁场,并获得百kJ/mm量级的能量输出。     

Ion separation due to magnetic field penetration into a multispecies plasma

The magnetic field, the electron density, and the ion velocities in a multispecies plasma conducting a high fast-rising current are determined using simultaneous spectroscopic measurements. It is found that ion separation occurs in which a light-ion plasma is pushed ahead while a heavy-ion plasma lags behind the magnetic piston. We show that most of the momentum imparted by the magnetic field pressure is taken by the reflected light ions, and most of the dissipated magnetic field energy is converted into kinetic energy of these ions, even though their mass is only a small part of the total plasma mass. Such species separation with implications to the momenta and energy partitioning is shown to be of a general nature.     

Luminescence due to exciton-exciton collision in GaAs

Emission spectra of high-purity GaAs have been studied at 4.2 K under N₂ laser excitation. The slope of the low-energy tail of the main band has been found to fit well with the theoretical prediction for radiative Auger recombination of free excitons. Measurements under electric field support the dominant contribution of this process in the luminescence of highly excited GaAs.     

Conformity between linear response and binary collision treatments of an ion energy loss in a magnetized quantum plasma

In this paper the energy loss of a heavy ion moving in a magnetized quantum electron plasma is considered within the linear response and binary collision treatments. Treating the electron-ion interaction force as a small perturbation to the electron nth Landau level we show within the second order perturbation theory the conformity between these two models.Received: 8 August 2003PACS: 52.40.Mj Particle beam interactions in plasmas - 34.50.Bw Energy loss and stopping power - 03.65.Nk Scattering theory - 52.20.Hv Atomic, molecular, ion, and heavy-particle collisions     

Nonsolid rotation of structures in isothermal magnetized atmospheres

Possible equilibrium rotating magnetized plasma configurations in which angular asymmetry due to a nonuniform distribution of the molecular weight is absent are studied. The viscosity of the medium is assumed to be negligible. The variables in exact nonlinear equations are separated by representing the vector fields as series in orthogonal vector spherical harmonics. These series are normally divergent. However, the truncation of the series is also possible. Equilibrium models corresponding to the truncated series are generalizations of a simple rigidly rotating model. They are studied below. It is shown that nonaxisymmetric equilibrium structures with the magnetic field of a tilted dipole are possible. In the case of an isothermal atmosphere, conditions for the superrotation of the medium and meridional circulation of the matter may arise. The feasibility of such conditions in the Earth’s upper atmosphere is discussed.     

Ion collection by oblique surfaces of an object in a transversely flowing strongly magnetized plasma

The equations governing a collisionless obliquely flowing plasma around an ion-absorbing object in a strong magnetic field are shown to have an exact analytic solution even for an arbitrary (two-dimensional) object shape, when temperature is uniform, and diffusive transport can be ignored. The solution has an extremely simple geometric embodiment. It shows that the ion collection flux density to a convex body's surface depends only upon the orientation of the surface and provides the theoretical justification and calibration of oblique "Mach probes." The exponential form of this exact solution helps explain the approximate fit of this function to previous numerical solutions.     

Sheath and plasma parameters in a magnetized plasma system

The variation of electron temperature and plasma density in a magnetized N₂ plasma is studied experimentally in presence of a grid placed at the middle of the system. Plasma leaks through the negatively biased grid from the source region into the diffused region. It is observed that the electron temperature increases with the magnetic field in the diffused region whereas it decreases in the source region of the system for a constant grid biasing voltage. Also, investigation is done to see the change of electron temperature with grid biasing voltage for a constant magnetic field. This is accompanied by the study of the variation of sheath structure across the grid for different magnetic field and grid biasing voltage as well. It reveals that with increasing magnetic field and negative grid biasing voltage, the sheath thickness expands.     

Faraday rotation due to quadratic gravitation

The linearized field equations of quadratic gravitation in stationary space-time are written in quasi-Maxwell form. The rotation of the polarization plane for an electromagnetic wave propagating in the gravito-electromagnetic field caused by a rotating gravitational lens is discussed. The influences of the Yukawa potential in quadratic gravitation on the gravitational Faraday rotation are investigated.     

Ballooning vortex in a magnetized plasma

The existence of a ballooning solitary vortex in an inhomogeneous plasma immersed in crossed magnetic and gravitational fields is demonstrated.