磁化等离子体环境对氢原子能级结构的影响

本文通过非微扰求解薛定谔方程, 研究了强磁场磁化的等离子体环境中的原子能级结构和辐射动力学过程. 在较宽的磁场强度范围和等离子体屏蔽参数范围内, 给出了氢原子基态以及低激发态的能级、辐射跃迁能量和振子强度等重要的原子参数, 定量地描述了强磁场和等离子体屏蔽共同作用的综合效应. 相关的结果有助于增进对极端环境下原子光谱结构的认识, 在等离子体光谱诊断和天文光谱观测方面有一定的借鉴意义. 关键词： 强磁场 CWDVR谱方法 能级结构 振子强度     

Stability of small planar dust cluster in the presence of an external magnetic field

Oscillations and stability of planar symmetric dust clusters shaped as a regular polygon and a regular polygon with a particle at the center in the presence of an external uniform magnetic field are analyzed. The structure stability against small perturbations is considered. To this end, the equation of motion was linearized with respect to small coordinate variations. As a result, a dispersion relation (quartic algebraic equation) was derived and numerically studied for particular types of interactions between particles. A comparison of stability regions for a quadrangle and a triangle with a particle at the center, as well as a pentagon and a quadrangle with a particle at the center shows that there are ranges of parameters, where configurations without particle at the center are stable and configurations with a particle at the center are unstable, and vice versa.     

Implosion of plasma liners in the presence of an axial magnetic field

Based on a radiative magnetohydrodynamic model, a numerical investigation is made of the implosion of single- and two-stage plasma liners with an initial axial magnetic field. The radiative magnetohydrodynamic model includes the equations of two-temperature hydrodynamics taking into account the electron and ion thermal conductivity, the electromagnetic field equations, and the equations of radiative transfer in a nonequilibrium medium. It is shown that in the case of a single-stage liner the implosion takes place in a subsonic regime, while the dynamics of a two-stage liner is determined by that of the propagation of shock waves of various intensities through the inner stage. Institute of High-Current Electronics, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 6–15. December, 1995.     

Slow waves in plasma waveguides in the presence of an azimuthal magnetic field

Abstracts of Deposited Articles.     

Pair production from hot plasma in the presence of a strong magnetic field

Acta physica Academiae Scientiarum Hungaricae - Radiation loss due to pair production by an intense electromagnetic wave is calculated. The calculations were made in the coulomb field of the ions...     

Penetration of probe field in heated plasma

Dependences of the effective penetration depth of probe pulse field in current-carrying plasma with time-dependent temperatures of particles are determined. It is shown that the field penetration in fully and weakly ionized plasmas takes place in the subdiffusion and superdiffusion regimes, respectively.     

Effects of axial magnetic field and nonextensivity on small amplitude dust acoustic solitary waves in dusty plasma

The nonlinear propagation of small amplitude dust‐acoustic (DA) solitary waves in magnetized dusty plasma consisting of negatively charged mobile dust fluid, and Boltzmann‐distributed electrons and ions with two distinct temperatures following a q‐nonextensive distribution are investigated. In this article, a number of nonlinear equations, namely, the Korteweg–de‐Vries (K‐dV) equations, have been derived by employing the reductive perturbation technique that is valid for a small but finite amplitude limit. The effects of nonextensivity of ions with two distinct temperatures and dust concentration on the amplitude and width of DA solitary waves are investigated theoretically. It is observed that both the nonextensive and low‐temperatures ions significantly modify the basic properties and polarities of DA solitary waves. It is shown that both positive and negative potential DA solitons occur in this case. The implications of these results to some astrophysical environments and space plasmas (e.g., stellar polytropes, peculiar velocity distributions of galaxies, and collisionless thermal plasma), and laboratory dusty plasma systems are briefly mentioned.     

Study on blood flow containing nanoparticles through porous arteries in presence of magnetic field using analytical methods

In this paper, flow analysis for a third grade non-Newtonian blood in porous arteries in presence of magnetic field is simulated analytically and numerically. Blood is considered as the third grade non-Newtonian fluid containing nanoparticles. Collocation Method (CM) and Optimal Homotopy Asymptotic Method (OHAM) are used to solve the Partial Differential Equation (PDE) governing equation which a good agreement between them was observed in the results. The influences of the some physical parameters such as Brownian motion parameter, pressure gradient and thermophoresis parameter, etc. on temperature, velocity and nanoparticles concentration profiles are considered. For instance, increasing the thermophoresis parameter (N_t) caused an increase in temperature values in whole domain and an increase in nanoparticles concentration near the inner wall.     

Persistent currents and induced magnetization in presence of external magnetic field and transition probabilities in presence of combined laser pulse and external magnetic field for a confined hydrogen atom

In this work we propose to study an atom confined in a potential which consists of a Hulthén potential plus a ring-shaped potential. The atom is further subjected to a spherical confinement. The time-independent Schrödinger equation (TISE) of the system is solved numerically. Exact energy levels are obtained. The persistent current and induced magnetic field of such a confined atom is evaluated. Finally, the atomic system in this potential and confinement is subjected to short electromagnetic pulses, which are shown to induce enormous currents.     

调制磁场清除柱形等离子体发生器中的尘埃颗粒

利用流体模型，计算了调制磁场作用下，圆柱形等离子体发生器中电子、离子及尘埃的运动情况．数值模拟结果表明，尘埃颗粒随着调制磁场频率的改变，产生两种不同的运动方式：pulse运动和除尘运动．解释了pulse运动产生的机理，并提出了柱形等离子体发生器中利用调制磁场清除尘埃颗粒的方法． 关键词： 尘埃颗粒 调制磁场     

Diffusion measurements at long observation times in the presence of spatially variable internal magnetic field gradients

Diffusion measurements in heterogeneous media may contain a significant source of error, the influence of the coupling between the applied and internal magnetic field gradients on the attenuation of the NMR signal. The application of bipolar magnetic field gradients has been introduced to suppress this error. The basic assumption for the successful removal of the coupling is that the diffusing molecules are experiencing a constant internal gradient during the experiment. We will provide theoretical and experimental evidence that the application of bipolar magnetic field gradients may fail to suppress the effect from all the cross terms between internal and applied gradients effectively at long observation times. It will be shown experimentally that a successful suppression of the cross terms is strongly dependent on the observation time, and on the tau value in the bipolar pulsed field gradient stimulated echo experiment. Copyright 2000 Academic Press.     

Collisionless damping of plasma waves in the presence of moderate density and magnetic field gradients

The propagation and damping of small amplitude quasi-longitudinal plasma waves in hot plasma in the presence of moderate density and magnetic field gradients is studied.     

Ion drag as a mechanism of plasma dust structure rotation in a strata in a magnetic field

In experiments on complex plasmas, afixed strata region in which the levitation of dust structures is observed is investigated using the method of probing by calibrated dust particles of different sizes in an applied magnetic field under elevated pressures. The measured azimuthal velocity of the probing particles corresponds to the action of the ion drag force for 4 μm-size particles and to the entrainment by the rotating gas owing to the electron vortex flow inside the strata for 1 μm-size particles. Extrapolation to pressures and magnetic fields in which the rotation inversion of dust structures is observed in experiments shows that the ion drag is the dominating force causing rotation with a negative projection of the angular velocity onto the magnetic induction.     

The effect of magnetic field on plasma particles in dusty plasma

In this work, we present the investigation of the formation features and internal structure of dust clouds created in plasma of glow discharge in the external magnetic field corresponding to a range of moderate and strong fields, at which the ion component is magnetized. The analysis of the plasma magnetization in the presence of dust components is carried out. We defined the values of magnetic induction at which the changes in dynamics of plasma particles in magnetic field in light inert gases are expected. The experimental setup was built in two versions. For the purpose of generating of magnetic field, the first setup was equipped with ordinary magnetic coils, and the second one included a superconducting solenoid. The discharge tubes, the main chambers where plasma was ignited and maintained in a glow discharge in lowered pressure, also have certain peculiarities, which we describe below. While using helium as a bulk gas, our study focused only on the dust trap in the region of narrowing discharge current. For neon, we used two traps: the striation trap and one just mentioned above placed in the narrowing of the discharge tube. As a result, the steady dust structures in a glow discharge under the magnetization of ions and electrons were obtained for the first time. Dust structures were rotated and tended to form a dust cluster and shell structure. A number of parameters of magnetization achieved in experiments were calculated.     

Relativistic excitation of beat waves in a plasma in the presence of an external magnetic field

Summary A theoretical investigation of the nonlinear relativistic excitation of the longitudinal electron plasma wave at the beat frequency of two colinear laser beams has been made in a hot, collisionless and homogeneous plasma in the presence of an external magnetic field. The relativistic Vlasov equation has been solved to obtain the nonlinear response of magnetized electrons. It is observed that the power conversion efficiency of the excited-electron plasma wave at the difference frequency is much higher for the relativistic calculation than that for the nonrelativistic calculations. It is further noticed that the power conversion efficiency of the beat wave excitation increases slowly with the external magnetic field when the colinear laser beams propagate transverse to the direction of the external magnetic field, whereas it is almost unaffected when the incident waves propagate parallel to the direction of the magnetic field.

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Riassunto Si è effettuata una ricerca teorica dell'eccitazione relativistica nonlineare dell'onda longitudinale del plasma dell'elettrone ad una frequenza di battimento di due raggi laser colineari in un plasma omogeneo, caldo e senza collisioni, in presenza di un campo magnetico esterno. è stata risolta l'equazione di Vlasov relativistica per ottenere la risposta nonlineare di elettroni magnetizzati. Si osserva che l'efficacia di conversione di potenza dell'onda di plasma degli elettroni eccitati alla frequenza di differenza è molto superiore per il calcolo relativistico che quella per i calcoli non relativistici. Si nota inoltre che l'efficacia di conversione di potenza dell'eccitazione d'onda di battimento aumenta lentamente con il campo magnetico esterno quando i raggi laser colineari si propagano trasversalmente rispetto alla direzione del campo magnetico esterno, mentre rimane quasi immutata quando le onde incidenti si propagano parallelamente alla direzione del campo magnetico.

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Резюме Проводится теоретическое исследование нелинейного релятивистского возбуждения продольных электронных плазменных волн на частоте биений двух соосных лазерных пучков в торячей, бесстолкновительной и однородной плазме в присутствии внешнего магнитного поля. Чтобы получить нелинейный отклик электронов в магнитном поле, решается релятивистское уравнение Власова. Получается, что эффективность конверсии мощности для возбужденной электронной плазменной волны на разностной частоте оказывается много большей для релятивистских вычислений, чем для нерелятивистских вычислений. Затем отмечается, что эффективность возбуждения биений увеличивается медленно с ростом внешнего магнитного поля, когда соосные лазерные пучки распространяются поперек направления внешнего магнитного поля, тогда как эффективность возбуждения почти не изменяется, когда падающие волны распространяются параллельно направлению магнитного поля.

     

Acceleration of electrons in an underdense plasma containing fluctuations of magnetic field on a background of a large scale dc-magnetic field

It is shown that scattering of electrons off magnetic field fluctuations can result in acceleration of these electrons along the lines-of-force of a large scale background dc-magnetic field. The mechanism proposed is applied to the underdense corona of a large scale produced plasma.