共查询到20条相似文献,搜索用时 31 毫秒
1.
Yu. P. Zakharov V. M. Antonov E. L. Boyarintsev A. V. Melekhov V. G. Posukh I. F. Shaikhislamov V. V. Pickalov 《Plasma Physics Reports》2006,32(3):183-204
The interaction of an expanding laser plasma with a uniform external magnetic field is studied over a wide range of experimental parameters (for a plasma energy of up to 300 J and a magnetic induction of up to 8 kG). By analyzing the data from these and other experiments, as well as the results of simulations with the use of a two-fluid Hall plasma model, it was found for the first time that the flute instability of the plasma boundary plays a decisive role in the process of the plasma cloud expansion. It is shown that, when the ion Larmor radius is sufficiently large, this instability can significantly affect the maximum radius of the diamagnetic cavity of the plasma cloud and the deceleration of its front by the magnetic field. A physical model based on the Hall effect is proposed to explain such influence. The model adequately describes data from one-dimensional simulations, as well as from experiments with quasi-spherical laser plasma clouds. The results obtained can be helpful in interpreting the data from active magnetospheric experiments with barium plasma clouds (such as AMPTE) and analyzing the plasma dynamics in future ICF reactors and propulsion systems with a magnetic field for direct conversion of fusion energy into electric energy. 相似文献
2.
A. N. Kozlov 《Plasma Physics Reports》2012,38(1):12-21
Near-electrode processes in a coaxial plasma accelerator with equipotential impenetrable electrodes are simulated using a
two-dimensional (generally, time-dependent) two-fluid MHD model with allowance for the Hall effect and the plasma conductivity
tensor. The simulations confirm the theoretically predicted mechanism of the so-called “crisis of current” caused by the Hall
effect. The simulation results are compared with available experimental data. The influence of both the method of plasma supply
to the channel and an additional longitudinal magnetic field on the development of near-electrode instabilities preceding
the crisis of current is studied. 相似文献
3.
A biophysical explanation of the reduced excitability in neurons exposed to a constant magnetic field is based on an extended neuronal membrane model. In the presence of a constant magnetic field, reduced excitability is manifested as an increase in the excitation threshold and a decrease in the frequency of action potentials. The proposed explanation for the reduced excitability rests on the well-known Hall effect. The separation of charges resulting from the Lorentz force exerted on moving intracellular ions leads to the formation of a Hall electric field in a direction perpendicular to that of action-potential transmission. Consequently, the ion current for discharging the membrane capacitance is reduced in the presence of a magnetic field, thereby limiting initiation of the action potential. The validity of the proposed biophysical explanation is justified analytically and verified by simulations based on the Hodgkin and Huxley model for the electrical excitability of a neuron. Based on derivation of the current segregation ratio α characterizing the reduction in the stimulating current from first principles, the equivalent circuit model of the neuronal membrane is extended to account for the reduced excitability of neurons exposed to a constant magnetic field. 相似文献
4.
S. Yu. Bogdanov G. V. Dreiden V. S. Markov G. V. Ostrovskaya A. G. Frank 《Plasma Physics Reports》2007,33(11):930-941
Two-exposure holographic interferometry was used to study the structure of current sheets formed in three-dimensional magnetic configurations with a singular X line in heavy noble gases (Ar, Kr, and Xe). It is found that, in the presence of a longitudinal magnetic field B Z directed along the X line, plasma sheets take on an unusual shape: they are titled and asymmetric. Their asymmetry becomes more pronounced as the mass of a plasma ion increases—a manifestation of the two-fluid properties of the plasma. The observed effects can be attributed to additional forces arising due to the interaction of the longitudinal magnetic field B Z with Hall currents excited in a plane perpendicular to the X line. A qualitative model describing plasma dynamics with allowance for the Hall effect and accounting for most of the experimentally observed effects is proposed. 相似文献
5.
V. V. Prudskikh 《Plasma Physics Reports》2011,37(10):871-880
A criterion for the development of a magnetorotational instability in a weakly ionized dusty plasma is considered. A dispersion
relation for the wavenumber and the growth rate of an unstable perturbation is derived for an arbitrary angle between the
wave vector and magnetic field. It is shown that the presence of dust grains can reverse the direction of the Hall current
in the plasma and can shift the instability threshold to shorter wavelengths. Under certain conditions, Alfvén fluctuations
of arbitrary scale can be unstable. The Hall current reversal is found to have a strong effect on the development of a magnetorotational
instability when the Alfvén resonance frequency in a weakly ionized plasma is close to the rotation frequency of the accretion
disk. 相似文献
6.
7.
S. F. Garanin 《Plasma Physics Reports》2000,26(4):283-291
A study is made of the motion of a plasma with a frozen-in magnetic field along the electrode surfaces in the direction transverse to the magnetic field. A one-dimensional problem of an electrode sheath is formulated in which all of the quantities depend only on the coordinate orthogonal to the electrode surface. Viscous plasma heating, plasma cooling via heat conduction, and other kinetic effects are taken into consideration. Account is also taken of the effect of plasma acceleration and of the related current that is transverse to the electrode surfaces and, due to the Hall effect, carries the magnetic flux away from the cathode and toward the anode. Solving the one-dimensional problem with a constant electric current and constant magnetic field shows that, in a sheath that forms near the cathode, the solution becomes self-similar, the plasma mass grows linearly, and the electron magnetization parameter remains unchanged. It is found that the anode sheath cannot be described in the magnetohydrodynamic approximation, according to which the plasma density in the sheath rapidly vanishes, while the current through the sheath remains constant. This difficulty can be overcome by incorporating some of the nonhydrodynamic effects (primarily, electron dispersion), thereby making the problem physically correct. Solving the problem numerically shows that a decrease in the plasma density in the anode sheath due to the Hall effect gives rise to additional significant plasma acceleration. 相似文献
8.
It is shown that plasma rotation near the tokamak the wall can result in a shift of the isobaric separatrix with respect to the magnetic one. This shift is calculated analytically, and this effect is exemplified by simple plasma equilibrium states. The plasma rotation that causes the shift of the separatrices can be driven either by a nonzero radial electric field at the plasma edge or by the Hall effect, which may take place even in the absence of the electric field. 相似文献
9.
V. V. Prudskikh 《Plasma Physics Reports》2014,40(5):380-388
Magnetorotational instability of a weakly ionized accretion disk with an admixture of charged dust grains in a magnetic field with the axial and toroidal components is analyzed. The dispersion relation for perturbations perpendicular to the disk plane is derived with allowance for both the Hall current and the finite transverse plasma conductivity. It is shown that dust grains play an important role in the disk magnetic dynamics. Due to the effect of dust grains, the Hall current can reverse its direction as compared to the case of electron-ion plasma. As a result, the instability threshold shifts toward the short-wavelength range. Under certain conditions, electromagnetic fluctuations of any length can become unstable. It is established that the instability criterion for waves of any scale length is satisfied within a finite interval of the density ratio between the dust and electron plasma components. The width of this interval and the instability growth rate as functions of the plasma parameters and the configuration of the magnetic field in the disk are analyzed. 相似文献
10.
The spatiotemporal dynamics of plasma sheets formed in argon plasma in two- and three-dimensional magnetic configurations with an X-type singular line was studied using holographic interferometry. An analogy is revealed between the development of plasma sheets and the time evolution of the current sheet structure, which was previously studied using magnetic measurements. In the late stage of the sheet evolution, a change in the rotation direction of plasma sheets formed in 3D magnetic configurations was observed. Apparently, this is caused by a change in the direction of the Hall currents at the side edges of the current sheet. 相似文献
11.
12.
A. F. Aleksandrov K. V. Vavilin E. A. Kral’kina V. B. Pavlov A. A. Rukhadze 《Plasma Physics Reports》2007,33(9):733-745
Results are presented from experimental studies of low-pressure inductive RF discharges (including those with a capacitive component) employed in plasma technology. It is shown that both the RF power absorbed in the plasma and the electron density depend nonmonotonically on the external magnetic field. Discharge disruptions occurring at critical values of the magnetic field and the spatial redistribution and hysteresis of the plasma parameters were observed when varying the magnetic field and RF generator power. The parameters of the plasma of low-pressure (0.5–5 mTorr) inductive RF discharges were investigated, and the discharge properties related to the redistribution of the RF generator power between the plasma and the discharge external circuit were revealed. The experiments were performed with both conventional unmagnetized inductive plasma sources and plasma sources with a magnetic field. 相似文献
13.
A simple model to determine the interrelation between the integral characteristics of hall thrusters
A simple model to determine the interrelation between the integral characteristics of Hall thrusters with an anode layer is proposed. The model includes the equation describing the balance of forces acting on the Hall current region, as well as the relationship between the current of accelerated ions and the rate of working gas consumption. For fixed geometrical characteristics of a specific Hall thruster, this model allows one to interrelate the main integral characteristics of the thruster, such as the accelerating voltage, the magnetic field, the propellant flow rate, and the current of accelerated ions. The results of calculations for TAL-WSF/D-55—one of the most widely used Hall thrusters with an anode layer—are presented. The domain of existence of the discharge in the channel of the Hall thruster is analyzed. It is shown that taking into account kinetic effects of neutral particle expansion and working gas preheating lead to a decrease in the current of accelerated ions and the engine thrust. 相似文献
14.
The problem is considered of configurations of a strongly magnetized inviscid plasma around a rotating magnetized central body. Strong plasma magnetization implies that the Hall conductivity is much lower than the transverse conductivity, which in turn is much lower than the longitudinal conductivity. For such conditions, a self-consistent set of equations is derived that describes the conduction current density, the magnetic and electric fields, and the angular frequency of the plasma rotation under the assumptions that the components of the dielectric tensor of the plasma envelope are known functions of height and that the plasma mass velocity has only the azimuthal component. Under the assumption that the transverse conductivity is constant over a magnetic surface, the nonlinear equations derived are solved in quadratures within the class of angular frequency distributions that are symmetric about the equatorial plane. A particular solution for the plasma configurations in a dipole magnetic field is considered that corresponds to a model exponential dependence of the transverse conductivity on the number of the L-envelope (or, equivalently, on the number of the unperturbed magnetic surface). 相似文献
15.
A. V. Zobnin A. P. Nefedov V. A. Sinel’shchikov O. A. Sinkevich A. D. Usachev V. S. Filinov V. E. Fortov 《Plasma Physics Reports》2000,26(5):415-423
Results are presented from the experimental studies and numerical simulations of the behavior of dust grains in the plasma
of an inductive RF discharge. The experiments were carried out with neon at a pressure of 25–500 Pa and with 1.87-μm melamine
formaldehyde grains. The discharge was excited by a ring inductor supplied from a generator operating at a 100-MHz frequency.
The effective dust-grain interaction potential used in numerical simulations involved the spatial dependence of the grain
charge on the plasma floating potential, grain-interaction anisotropy resulting from the focusing of the drift ion current
by the negatively charged grains, and specific features of the shielding of the dust grains by the plasma electrons and ions
recombining both in the plasma bulk and on the grain surface. The results of Monte Carlo simulations show that the dust grains
form specific filament structures observed experimentally in the plasma of an inductive electrodeless discharge.
__________
Translated from Fizika Plazmy, Vol. 26, No. 5, 2000, pp. 445–454.
Original Russian Text Copyright ? 2000 by Zobnin, Nefedov, Sinel’shchikov, Sinkevich, Usachev, Filinov, Fortov. 相似文献
16.
V. V. Prudskikh 《Plasma Physics Reports》2013,39(12):1004-1010
The propagation of low-frequency electromagnetic waves along the magnetic field in weakly ionized plasma with an admixture of dust is studied in the framework of the Hall magnetohydrodynamics. Explicit expressions for the coefficients of magnetic field diffusion in plasma are derived. The resonance of the refractive index is found to occur for either right- or left-hand polarized waves. A quantitative criterion is obtained that allows one to determine the polarization of waves that experience resonance at given plasma parameters. The physical mechanism of the resonance is discussed, and the obtained results are compared with the available literature data. 相似文献
17.
V. B. Krasovitskii V. G. Dorofeenko V. A. Turikov V. I. Sotnikov 《Plasma Physics Reports》2006,32(1):25-31
The decay instability of a lser pulse propagating across an external magnetic field in a subscritical plasma is investigated analytically and numerically. It is shown that, when the relaxation of the pulse is taken into account, the hydrodynamic growth rate of the decay instability is slower than that obtained earlier in the constant-amplitude pump wave approximation. The results of numerical simulations by a particle-in-cell method demonstrate that an increase in the amplitude of the parametrically excited waves is accompanied by a decrease in their group velocity; in this case, up to 85% of the laser energy is converted into the energy of the plasma particles. It is found that, under resonance conditions, the magnetic field acts to increase the energy of the accelerated ions that escape from the plasma slab through its front boundary. 相似文献
18.
V. Urpin 《Plasma Physics Reports》2017,43(3):307-314
Diffusion caused by a combined influence of the electric current and Hall effect is considered, and it is argued that such diffusion can form inhomogeneities of a chemical composition in plasma. The considered mechanism can be responsible for the formation of element spots in laboratory and astrophysical plasmas. This current-driven diffusion can be accompanied by propagation of a particular type of waves in which the impurity number density oscillates alone. These compositional waves exist if the magnetic pressure in plasma is much greater than the gas pressure. 相似文献
19.
The propagation of a nonlinear right-hand polarized wave along an external magnetic field in subcritical plasma in the electron cyclotron resonance region is studied using numerical simulations. It is shown that a small-amplitude plasma wave excited in low-density plasma is unstable against modulation instability with a modulation period equal to the wavelength of the excited wave. The modulation amplitude in this case increases with decreasing detuning from the resonance frequency. The simulations have shown that, for large-amplitude waves of the laser frequency range propagating in plasma in a superstrong magnetic field, the maximum amplitude of the excited longitudinal electric field increases with the increasing external magnetic field and can reach 30% of the initial amplitude of the electric field in the laser wave. In this case, the energy of plasma electrons begins to substantially increase already at magnetic fields significantly lower than the resonance value. The laser energy transferred to plasma electrons in a strong external magnetic field is found to increase severalfold compared to that in isotropic plasma. It is shown that this mechanism of laser radiation absorption depends only slightly on the electron temperature. 相似文献
20.
N. U. Barinov S. A. Budkov G. I. Dolgachev D. D. Maslennikov I. A. Khodeev 《Plasma Physics Reports》2002,28(3):177-182
The influence of an external magnetic field on the performance of a high-impedance plasma opening switch is studied experimentally. A 1.5-fold increase in the output voltage of a plasma opening switch operating in the erosion mode is achieved by applying an external magnetic field. The magnetic field strength and the parameters of the plasma opening switch at which the maximum output voltage is attained are determined. It is shown experimentally that the predicted dependence of the maximum output voltage on the Marx generator voltage, U POS [MV]=3.6 (U MG [MV])4/7, is confirmed experimentally. 相似文献