Magnetic resonance in an inhomogeneous rotational solenoidal field

Specific features of magnetic resonance and relaxation are investigated in the magnetic field set up by the current flowing through the specimen. It is shown that: a) if the field is a magnetizing field, then the components perpendicular to the current, of the macroscopic magnetization are identically zero and b) if it is a resonance field, the power absorbed increases with an increasing saturation factor.     

Electron hole generation and propagation in an inhomogeneous collisionless plasma

The generation of "trains" of electron holes in phase space due to an external electrostatic disturbance is investigated by using a Vlasov-Ampere code with open boundary conditions. Electron holes are produced mostly during the initial phase of the wave-plasma interaction, with a given drift velocity which is maintained until they exit the integration box, even in the presence of plasma inhomogeneities. They present macroscopic features, a dipolar electrostatic field and an electron density perturbation, which can be exploited for diagnostic purposes. Their equilibrium is intrinsically kinetic, in that they are accompanied by a stationary hole in the electron distribution function.     

Magnetic domain wall dynamics in an inhomogeneous magnetic field

A new experimental method for the study of single magnetic domain wall dynamics in bistable microwires is presented. It raises new possibilities for experimenting with a single magnetic domain wall moving in an inhomogeneous magnetic field. Models for a wall with fixed length were confronted with experimental data obtained on amorphous glass-coated ferromagnetic Fe_77.5B₁₅Si_7.5${\mathrm{Fe}}_{77.5}{\mathrm{B}}_{15}{\mathrm{Si}}_{7.5}$ microwire. These models qualitatively describe the observed behavior. The accord between models and experiment increases as the field disturbance decreases due to its inhomogeneity. A better match between experimental and model curves can probably be obtained if the changes in the wall dimensions and wall mass are taken into account.     

Magnetic field annihilation and reconnection driven by femtosecond lasers in inhomogeneous plasma

The process of fast magnetic reconnection driven by intense ultra-short laser pulses in underdense plasma is investigated by particle-in-cell simulations. In the wakefield of such laser pulses, quasi-static magnetic fields at a few mega-Gauss are generated due to nonvanishing cross product ▽(n/) × p. Excited in an inhomogeneous plasma of decreasing density, the quasi-static magnetic field structure is shown to drift quickly both in lateral and longitudinal directions. When two parallel-propagating laser pulses with close focal spot separation are used, such field drifts can develop into magnetic reconnection(annihilation) in their overlapping region, resulting in the conversion of magnetic energy to kinetic energy of particles. The reconnection rate is found to be much higher than the value obtained in the Hall magnetic reconnection model. Our work proposes a potential way to study magnetic reconnection-related physics with short-pulse lasers of terawatt peak power only.     

Propagation and reflection of an electromagnetic wave in a hot inhomogeneous plasma

Using the WKB method a local dispersion equation of a right-hand circularly polarized wave and an expression for its electric field are derived, the wave having frequency smaller than the electron cyclotron frequency and propagating in a hot inhomogeneous plasma. The density gradient of the plasma is constant and parallel to an external magnetostatic field. Further the reflection coefficient of this wave is derived.Stimulating discussions with Dr. J. Václavík are gratefully acknowledged.     

Magnetic instability in an inhomogeneous plasma in an intense electromagnetic wave

Radiophysics Research Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 33, No. 2, pp. 170–176, February, 1990.     

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.     

Effect of external magnetic field on nonlinear propagation of cylindrical magnetoacoustic soliton waves in quantum plasma

The propagation of magnetoacoustic solitary waves is investigated in magnetized quantum plasma consisting of cold ions and hot electrons. By using the quantum magnetohydrodynamic (QMHD) model, the nonlinear characteristics of different features of solitary waves in an electron-ion quantum magnetoplasma are investigated. Magnetoacoustic solitary waves are stationary solutions of the equations composed of the nonlinear mass and momentum continuity, together with the Maxwell's equations. The important quantum-mechanical effects including the quantum statistical and diffraction are examined numerically on the profiles of the solitons. It is found that the non-dimensional characteristic of the quantum parameter plays a significant role in the formation of the solitons.     

Electromagnetic soliton propagation in an anisotropic Heisenberg helimagnet

We study the nonlinear spin dynamics of Heisenberg helimagnet under the effect of electromagnetic wave (EM) propagation. The basic dynamical equation of the spin evolution governed by Landau–Lifshitz equation resembles the director dynamics of the twist in a cholestric liquid crystal. With the use of reductive perturbation technique the perturbation is invoked for the spin magnetization and magnetic field components of the propagating electromagnetic wave. A steady-state solution is derived for the weakly nonlinear regime and for the next order, the components turn around s plane perpendicular to the propagation direction. It is found that as the electromagnetic wave propagates in the medium, both the magnetization and magnetic field modulate in the form of kink soliton modes by introducing amplitude fluctuation in the tail part of the same.     

Magnetic field propagation in a stellar dynamo

Numerical simulations of stellar dynamos are reviewed. Dynamic dynamo models solve the nonlinear, three-dimensional, time-dependent, magnetohydrodynamic equations for the convective velocity, the thermodynamic variables, and the generated magnetic field in a rotating, spherical shell of ionized gas. When the dynamo operates in the convection zone, the simulated magnetic fields propagate away from the equator in the opposite direction inferred from the solar butterfly diagram. When simulated at the base of the convection zone, the fields propagate in the right direction at roughly the right speed. However, owing to the numerical difficulty, a full magnetic cycle has not been simulated in this region. As a result, it is still uncertain where and how the solar dynamo operates.     

On a generalized soliton solution as an inhomogeneous cosmological model

We consider a generalized vacuum soliton solution of Einstein's equations with three parameters. Depending on the values of the parameters it is the matching of the Kasner metric with a Wainwright, Ince and Marshman solution, the inhomogeneous version of some Bianchi III stiff matter metrics, and inhomogeneous (and homogeneous) space-times with the cosmological singularity only.Work partially supported by research project CAICYT.     

Magnetic field driven domain-wall propagation in magnetic nanowires

The mechanism of magnetic field induced magnetic domain-wall (DW) propagation in a nanowire is revealed: A static DW cannot exist in a homogeneous magnetic nanowire when an external magnetic field is applied. Thus, a DW must vary with time under a static magnetic field. A moving DW must dissipate energy due to the Gilbert damping. As a result, the wire has to release its Zeeman energy through the DW propagation along the field direction. The DW propagation speed is proportional to the energy dissipation rate that is determined by the DW structure. The negative differential mobility in the intermediate field is due to the transition from high energy dissipation at low field to low energy dissipation at high field. For the field larger than the so-called Walker breakdown field, DW plane precesses around the wire, leading to the propagation speed oscillation.     

Collisions in dispersion-managed soliton propagation

We study collisions in dispersion-managed soliton propagation for wavelength-division multiplexing application at zero net dispersion when the Gordon-Haus timing jitter is removed. We show that the collisions can lead to group-velocity changes and spectral collapse. Large channel separation ameliorates the effects. Filters prevent spectral collapse but do not affect the velocity changes.     

Characterization of microwave plasma generated in inhomogeneous magnetic field

The paper is devoted to the investigation of the electron cyclotron resonance (ECR) discharge in the decreasing magnetic field in the pressure range from 0.02 Pa to 90 Pa and the absorbed microwave power from 50 W to 400 W. For a discharge characterization we used the floating potentialU _fl and the saturated ion current densityi _sat ⁺ . The influence of the substrate holder presence on the plasma microparameters was studied. It was shown that for the substrate holder located near ECR at pressures below 0.3 Pa mainly the magnitude ofU _fl strongly depends on the pressurep, the absorbed microwave powerP _a, and the position of the substrate holder with respect to ECR. The values ofU _fl in the plasma in which the substrate holder is inserted strongly differ from those in the plasma without the substrate holder.U _fl of low pressuresp<0.05 Pa achieves high positive values of about +50 V and this results in sputtering of chamber walls.