Spontaneous Generation Of Magnetic Fields Research Articles

Spontaneous generation of magnetic fields in thin layers of stratified plasma

In this work, the processes of spontaneous generation of magnetic fields by Rayleigh–Benard convection in a thin layer of plasma in a constant gravitational field are investigated. The values of the critical Rayleigh number for stationary convection are obtained, and the criteria for the occurrence of instability leading to the generation of magnetic fields are determined within the framework of electron magnetic hydrodynamics (EMHD). The weakly nonlinear regime of magnetic fields generation is studied using the method of perturbation theory with respect to the small supercriticality parameter ε=(Ra−Rac)/Rac of the stationary Rayleigh number Rac. A nonlinear equation of the Ginzburg–Landau type is obtained, which describes the evolution of the stationary level of excited magnetic fields.

Magnetic field amplification driven by the gyro motion of charged particles

Spontaneous magnetic field generation plays important role in laser-plasma interactions. Strong quasi-static magnetic fields affect the thermal conductivity and the plasma dynamics, particularly in the case of ultra intense laser where the magnetic part of Lorentz force becomes as significant as the electric part. Kinetic simulations of giga-gauss magnetic field amplification via a laser irradiated microtube structure reveal the dynamics of charged particle implosions and the mechanism of magnetic field growth. A giga-gauss magnetic field is generated and amplified with the opposite polarity to the seed magnetic field. The spot size of the field is comparable to the laser wavelength, and the lifetime is hundreds of femtoseconds. An analytical model is presented to explain the underlying physics. This study should aid in designing future experiments.

Implementation of amplitude–phase analysis of complex interferograms for measurement of spontaneous magnetic fields in laser generated plasma

Generation of spontaneous magnetic fields (SMFs) is one of the most interesting phenomena accompanying an intense laser–matter interaction. One method of credible SMFs measurements is based on the magneto-optical Faraday effect, which requires simultaneous measurements of an angle of polarization plane rotation of a probe wave and plasma electron density. In classical polaro-interferometry, these values are provided independently by polarimetric and interferometric images. Complex interferometry is an innovative approach in SMF measurement, obtaining information on SMF directly from a phase–amplitude analysis of an image called a complex interferogram. Although the theoretical basis of complex interferometry has been well known for many years, this approach has not been effectively employed in laser plasma research until recently; this approach has been successfully implemented in SMF measurement at the Prague Asterix Laser System (PALS). In this paper, proprietary construction solutions of polaro-interferometers are presented; they allow us to register high-quality complex interferograms in practical experiments, which undergo quantitative analysis (with an original software) to obtain information on the electron density and SMFs distributions in an examined plasma. The theoretical foundations of polaro-interferometric measurement, in particular, complex-interferometry, are presented. The main part of the paper details the methodology of the amplitude–phase analysis of complex interferograms. This includes software testing and examples of the electron density and SMF distribution of a laser ablative plasma generated by irradiating Cu thick planar targets with an iodine PALS laser at an intensity above about 1016 W/cm2.

Proposed Spontaneous Generation of Magnetic Fields by Curved Layers of a Chiral Superconductor.

We demonstrate that two-dimensional chiral superconductors on curved surfaces spontaneously develop magnetic flux. This geometric Meissner effect provides an unequivocal signature of chiral superconductivity, which could be observed in layered materials under stress. We also employ the effect to explain some puzzling questions related to the location of zero-energy Majorana modes.

Kinetic magnetization by fast electrons in laser-produced plasmas at sub-relativistic intensities

The problem of spontaneous magnetic field generation with nanosecond laser pulses raises a series of fundamental questions, including the intrinsic magnetization mechanisms in laser-driven plasmas and the understanding of charge-discharge processes in the irradiated target. These two issues are tightly bound as the charge-discharge processes are defined by the currents, which have in turn a feedback by magnetic fields in the plasma. Using direct polaro-interferometric measurements and theoretical analysis, we show that at parameters related to the PALS laser system (1.315 μm, 350 ps, and 1016 W/cm2), fast electrons play a decisive role in the generation of magnetic fields in the laser-driven plasma. Spatial distributions of electric currents were calculated from the measured magnetic field and plasma density distributions. The obtained results revealed the characteristics of strong currents observed in capacitor-coil magnetic generation schemes and open a new approach to fundamental studies related to magnetized plasmas.

Spontaneous magnetic fields in the compressed plasma of a thermonuclear laser target

A model describing the generation of spontaneous magnetic fields (SMFs) in a laser thermonuclear target has been developed. The compression of a cryogenic laser target with a gain on the order of 1 is studied. Magnetic fields of 10–100 MG are generated in a compressed DT plasma. The possibility of observing these fields in such a plasma is discussed.

Progress in development of HEDP capabilities in FLASH’s Unsplit Staggered Mesh MHD solver

FLASH is a publicly available astrophysical community code designed to solve highly compressible multi-physics reactive flows. We are adding capabilities to FLASH that will make it an open science code for the academic HEDP community. Among many important numerical requirements, we consider the following features to be important components necessary to meet our goals for FLASH as an HEDP open toolset. First, we are developing computationally efficient time-stepping integration methods that overcome the stiffness that arises in the equations describing a physical problem when there are disparate time scales. To this end, we are adding two different time-stepping schemes to FLASH that relax the time step limit when diffusive effects are present: an explicit super-time-stepping algorithm (Alexiades et al. in Com. Num. Mech. Eng. 12:31–42, 1996) and a Jacobian-Free Newton-Krylov implicit formulation. These two methods will be integrated into a robust, efficient, and high-order accurate Unsplit Staggered Mesh MHD (USM) solver (Lee and Deane in J. Comput. Phys. 227, 2009). Second, we have implemented an anisotropic Spitzer-Braginskii conductivity model to treat thermal heat conduction along magnetic field lines. Finally, we are implementing the Biermann Battery term to account for spontaneous generation of magnetic fields in the presence of non-parallel temperature and density gradients.

Polarization-force-induced dust grain acceleration and intrinsic magnetization of dusty plasmas

AbstractIt is shown that the polarization force, arising from interactions between thermal ions and highly charged dust grains, can accelerate charged dust grains and can also create spontaneous magnetic fields in a quasi-neutral dusty plasma. The present results are relevant for understanding the origin of dust grain acceleration and the generation of spontaneous magnetic fields in cosmic dusty plasmas.

Dynamics of nonlinearly interacting magnetic electron drift vortex modes in a nonuniform plasma

A simulation study of dynamical evolution of nonlinearly interacting two-dimensional magnetic electron drift vortex (MEDV) modes in a nonuniform plasma is presented. Depending on the equilibrium density and temperature gradients, the system can either be stable or unstable. The unstable system reveals spontaneous generation of magnetic fields from noise level, and large-scale magnetic field structures are formed. When the system is linearly stable, one encounters MEDV mode turbulence in which there is a competition between zonons (zonal flows) and streamers. For large MEDV mode amplitudes, one encounters the formation of localized and small-scale magnetic vortices and vortex pairs with scale sizes of the order of the electron skin depth. The MEDV turbulence exhibits nonuniversal (non-Kolmogorov-type) spectra for different sets of plasma parameters. The relevance of this work to laboratory and cosmic plasmas is briefly mentioned.

Magnetization of left-handed metamaterials

We propose a possible mechanism for the generation of magnetic fields in negative refraction index composite metamaterials. Considering the propagation of a high-frequency modulated amplitude electric field in a left-handed material (LHM), we show that the ponderomotive interaction between the field and low-frequency potential distributions leads to spontaneous generation of magnetic fields, whose form and properties are discussed.

Controlled and spontaneous magnetic field generation in a gun-driven spheromak

In the Sustained Spheromak Physics Experiment, SSPX [E. B. Hooper, D. Pearlstein, and D. D. Ryutov, Nucl. Fusion 39, 863 (1999)], progress has been made in understanding the mechanisms that generate fields by helicity injection. SSPX injects helicity (linked magnetic flux) from 1 m diameter magnetized coaxial electrodes into a flux-conserving confinement region. Control of magnetic fluctuations (δB∕B∼1% on the midplane edge) yields Te profiles peaked at >200eV. Trends indicate a limiting beta (βe∼4%–6%), and so we have been motivated to increase Te by operating with stronger magnetic field. Two new operating modes are observed to increase the magnetic field: (A) Operation with constant current and spontaneous gun voltage fluctuations. In this case, the gun is operated continuously at the threshold for ejection of plasma from the gun: stored magnetic energy of the spheromak increases gradually with δB∕B∼2% and large voltage fluctuations (δV∼1kV), giving a 50% increase in current amplification, Itor∕Igun. (B) Operation with controlled current pulses. In this case, spheromak magnetic energy increases in a stepwise fashion by pulsing the gun, giving the highest magnetic fields observed for SSPX (∼0.7T along the geometric axis). By increasing the time between pulses, a quasisteady sustainment is produced (with periodic good confinement), comparing well with resistive magnetohydrodynamic simulations. In each case, the processes that transport the helicity into the spheromak are inductive and exhibit a scaling of field with current that exceeds those previously obtained. We use our newly found scaling to suggest how to achieve higher temperatures with a series of pulses.

Spontaneous generation of magnetic fields in astrophysical dusty plasmas

Two novel mechanisms for spontaneous generation of magnetic fields in dusty plasmas are presented. These are a new dust–plasma battery involving the cross product of the gradient of the dust charge density and the electron–ion pressures, as well as a new Weibel-like instability involving ion pressure anisotropy and resistive electron motions. The relevance of the present investigation to magnetic fields in astrophysical objects is discussed.

The spontaneous generation of magnetic fields at high temperature in a supersymmetric theory

The spontaneous generation of magnetic and chromomagnetic fields at high temperature in the minimal supersymmetric standard model (MSSM) is investigated. The consistent effective potential including the one-loop and the daisy diagrams of all bosons and fermions is calculated and the magnetization of the vacuum is observed. The mixing of the generated fields due to the quark and s-quark loop diagrams and the role of superpartners are studied in detail. It is found that the contribution of these diagrams increases the magnetic and chromomagnetic field strengths as compared with the case of a separate generation of fields. The magnetized vacuum state is found to be stable due to the magnetic masses of gauge fields included in the daisy diagrams. Applications of the results obtained are discussed. A comparison with the standard model case is done.

Numerical simulation of spontaneous magnetic fields in laser produced plasma jet using MAG code

The results of numerical simulation of spontaneous magnetic field generation and the influence of this field on laser produced plasma jet expansion in vacuum and low density gas are presented. The numerical simulation has been carried out using 2D MHD code for the case of an Al plate of 5 μm thickness irradiated by an Nd laser. The laser pulse duration was 0.5 ns at half-width, laser irradiation intensity was up to 1013 W/cm2 and laser focal spot diameter was about 100 μm. According to the received results, the magnetic field amplitude achieves the value of 150 kGs. This fact has no considerable influence on the temperature maximum in laser produced plasma, but significantly affects the process of the energy transport from plasma jet to low density gas. Shock wave generated magnetic field with reversal profile can be achieved in the case of plasma propagating into background gas.

Low regularity solutions for a generalized Zakharov system

Using the method of Bourgain (actually we use techniques developed in the paper of Ginibre, Tsutsumi, Velo (cf. [9])) we prove well-posedness of a generalized Zakharov system, describing the spontaneous generation of magnetic field in a cold plasma, in the framework of classical Sobolev spaces. Using the conservation laws of the system we extend these solutions globally in the energy space.

Spontaneous generation of magnetic field in three dimensional QED at finite temperature

We investigate the effects of thermal fluctuations on the spontaneous magnetic condensate in three dimensional QED coupled with P-odd Dirac fermions. Our results show that the phenomenon of the spontaneous generation of the constant background magnetic field survives to the thermal corrections even at infinite temperature. We also study the thermal corrections to the fermionic condensate in presence of the magnetic field.

Generation of currents and electromagnetic fields in an inhomogeneous laser plasma

A physical model of generation of spontaneous magnetic fields and of electric currents in an inhomogeneous laser plasma is developed for a wide range of laser radiation flux densities. It is shown that spontaneous magnetic fields generated in a plasma may be governed not only by the bulk emf sources, but can be influenced significantly by the processes at interfaces in a plasma (for example, at DT fuel–shell, plasma–metal, and other interfaces). A quasistationary approximation is used to formulate the boundary conditions governing the surface sources of spontaneous magnetic fields. A detailed analysis is made of an inhomogeneity of the potential of a double layer and of an effective contact emf in their role as surface mechanisms of generation of spontaneous magnetic fields. Generation of fields and currents is considered analytically in the region of an inhomogeneous interface between two plasmas and in an inhomogeneous laser jet formed as a result of interaction of laser radiation with a conducting target.

Some remarks on spontaneous magnetic field generation and the nonlinear dynamics of a Langmuir plasma

It is shown that, in the hydrodynamic approximation, the spontaneous generated magnetic field does not act directly on the development of Langmuir plasma turbulence. It is shown that besides the magneto-modulational effects, it is necessary to take into account the purely relativistic effect, i.e. the dependence of the electron mass on velocity. In most cases the contribution of this relativistic effect prevails over the spontaneous magnetic field contribution to the development of the modulational instability of HF waves.

Generation of ELF/ULF waves in the ionosphere by dynamo processes

It is shown that amplitude modulated HF heating in the ionospheric E-region, can produce substantial power in the ELF/UI range even in the absence of ambient ionospheric currents. The signals are associated with spontaneous generation of magnetic fields caused by the coupling of the hot spot temperature gradient to the ambient ionospheric density gradient (Vn x VT). The mechanism produces values for PC5 micropulsations consistent with those observed by Stubbe and Kopka (1981).

Spontaneous generation of magnetic field in an imploding plasma

Spontaneous generation of an axial magnetic field is predicted when the usually neglected centripetal acceleration term is properly taken into account in the two-fluid equations of motion for a cylindrically symmetric imploding plasma. An order-of-magnitude calculation is presented to illustrate spontaneous generation of a reversed-field configuration in a plasma imploded by a metallic liner.