Currents in the ideal frozen-in plasma moving with the velocity being arbitrary on the direction across the magnetic field

1992 ◽  
Vol 197 (2) ◽  
pp. 299-308 ◽  
Author(s):  
M. V. Samokhin
Keyword(s):  
Magnetic Field ◽  
The Magnetic Field ◽  
The Ideal

scholarly journals DYNAMO EFFECTS IN MAGNETIZED IDEAL PLASMA COSMOLOGIES

2008 ◽  
Vol 23 (11) ◽  
pp. 1697-1710 ◽  
Author(s):  
KOSTAS KLEIDIS ◽  
APOSTOLOS KUIROUKIDIS ◽  
DEMETRIOS PAPADOPOULOS ◽  
LOUKAS VLAHOS
Keyword(s):  
Magnetic Field ◽  
Cosmological Model ◽  
Homogeneous Magnetic Field ◽  
Mhd Equations ◽  
Cosmological Perturbations ◽  
Gravitational Instabilities ◽  
Ideal Magnetohydrodynamic ◽  
The Magnetic Field ◽  
Ideal Plasma ◽  
The Ideal

The excitation of cosmological perturbations in an anisotropic cosmological model and in the presence of a homogeneous magnetic field has been studied, using the ideal magnetohydrodynamic (MHD) equations. In this case, the system of partial differential equations which governs the evolution of the magnetized cosmological perturbations can be solved analytically. Our results verify that fast-magnetosonic modes propagating normal to the magnetic field, are excited. But, what is most important, is that, at late times, the magnetic-induction contrast(δB/B) grows, resulting in the enhancement of the ambient magnetic field. This process can be particularly favored by condensations, formed within the plasma fluid due to gravitational instabilities.

A new furnace for improving thermal demagnetization in paleomagnetism

2020 ◽  
Author(s):  
Huafeng Qin ◽  
Xiang Zhao ◽  
Shuangchi Liu ◽  
Greig Paterson ◽  
Zhaoxia Jiang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Curie Temperature ◽  
High Performance ◽  
Thermal Treatments ◽  
Thermal Demagnetization ◽  
Heating Wire ◽  
Low Magnetic Field ◽  
Detrimental Impact ◽  
The Magnetic Field ◽  
The Ideal

<p>Thermal demagnetization furnaces are routine facilities for paleomagnetic studies. The ideal thermal demagnetizer should maintain “zero” magnetic field during thermal treatments. However, magnetic field noises, including residual magnetic fields of material and induced fields caused by the heating current in the furnace are always present. The key to making high-performance demagnetization furnace is to reduce the magnetic field noises. By combining efficient demagnetization of shielding and a new structure of heating wire, we have developed a new demagnetization furnace with low magnetic field noises. Repeated progressive thermal demagnetization experiments using specimens that were previously completely thermal demagnetized above their Curie temperature were carry out to explore the effects of field within various types of furnace during demagnetization. These experiment confirm that magnetic field noises in the furnace can have an observable and detrimental impact on demagnetization behavior. Comparison between commercial furnaces and our new design show a notable reduction in the impacts of on thermal demagnetization behavior. The new heating element design and procedure for reducing magnetic field noises represent a significant improvement in the design of thermal demagnetizers and allows for extremely weak specimens to be successfully measured.</p>

scholarly journals Designing Iron Oxide Nanoparticles for Image Guided Thermal Medicine Applications

2019 ◽  
Author(s):  
Hattie Ring ◽  
Sheng Tong ◽  
Zhe Gao ◽  
Navid Manuchehrabadi ◽  
Kaiyi Jiang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Iron Oxide ◽  
Field Strength ◽  
Iron Oxide Nanoparticles ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Oxide Nanoparticles ◽  
Image Guided ◽  
The Magnetic Field ◽  
The Ideal

This work evaluates MRI relaxation and the specific absorption rate properties of iron oxide nanoparticles (IONPs) as a function of diameter (6-32 nm). We conclude that the ideal IONP diameter for image guided heating applications is dependent on the magnetic field strength of the MRI for the intended application. <br>

scholarly journals Thermal conduction effects on formation of chromospheric solar tadpole-like jets

2020 ◽  
Vol 500 (3) ◽  
pp. 3329-3334
Author(s):  
Anamaría Navarro ◽  
F D Lora-Clavijo ◽  
K Murawski ◽  
Stefaan Poedts
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Thermal Conduction ◽  
Mhd Equations ◽  
Temperature Model ◽  
Mass Fluxes ◽  
Parametric Studies ◽  
Atmospheric State ◽  
The Magnetic Field ◽  
The Ideal

ABSTRACT We measure the effects of non-isotropic thermal conduction on generation of solar chromospheric jets through numerical simulations carried out with the use of one fluid magnetohydrodynamics (MHD) code magnus. Following the work of Srivastava et al. (2018), we consider the atmospheric state with a realistic temperature model and generate the ejection of plasma through a gas pressure driver operating in the top chromosphere. We consider the magnetic field mimicking a flux tube and perform parametric studies by varying the magnetic field strength and the amplitude of the driver. We find that in the case of thermal conduction the triggered jets exhibit a considerably larger energy and mass fluxes and their shapes are more collimated and penetrate more the solar corona than for the ideal MHD equations. Low magnetic fields allow these jets to be more energetic, and larger magnetic fields decrease the enhancement of mass and energy due to the inclusion of the thermal conductivity.

scholarly journals Cosmic magnetic fields with masclet: an application to galaxy clusters

2020 ◽  
Vol 494 (2) ◽  
pp. 2706-2717
Author(s):  
Vicent Quilis ◽  
José-María Martí ◽  
Susana Planelles
Keyword(s):  
Magnetic Field ◽  
Galaxy Clusters ◽  
Adaptive Mesh Refinement ◽  
Adaptive Mesh ◽  
Pure Compression ◽  
Ideal Magnetohydrodynamics ◽  
Relative Errors ◽  
Cluster Values ◽  
The Magnetic Field ◽  
The Ideal

ABSTRACT We describe and test a new version of the adaptive mesh refinement cosmological code masclet. The new version of the code includes all the ingredients of its previous version plus a description of the evolution of the magnetic field under the approximation of the ideal magnetohydrodynamics (MHD). To preserve the divergence-free condition of MHD, the original divergence cleaning algorithm of Dedner et al. (2002) is implemented. We present a set of well-known 1D and 2D tests, such as several shock tube problems, the fast rotor, and the Orszag–Tang vortex. The performance of the code in all the tests is excellent with estimated median relative errors of ∇ · B in the 2D tests smaller than 5 × 10−5 for the fast rotor test, and 5 × 10−3 for the Orszag–Tang vortex. As an astrophysical application of the code, we present a simulation of a cosmological box of 40 comoving Mpc side length in which a primordial uniform comoving magnetic field of strength 0.1 nG is seeded. The simulation shows how the magnetic field is channelled along the filaments of gas and is concentrated and amplified within galaxy clusters. Comparison with the values expected from pure compression reveals an additional amplification of the magnetic field caused by turbulence in the central region of the cluster. Values of the order of ∼1µG are obtained in clusters at z ∼ 0 with median relative errors of ∇ · B below 0.4 per cent. The implications of a proper description of the dynamics of the magnetic field and their possible observational counterparts in future facilities are discussed.

Experiments on the superconductive transition

1949 ◽  
Vol 200 (1060) ◽  
pp. 66-84 ◽  
Keyword(s):  
Magnetic Field ◽  
Electrical Resistivity ◽  
Normal State ◽  
Longitudinal Magnetic Field ◽  
Geometrical Shape ◽  
Longitudinal Field ◽  
Experimental Procedure ◽  
Absolute Value ◽  
The Magnetic Field ◽  
The Ideal

The change of electrical resistivity at the transition between the superconductive and the normal state in a longitudinal magnetic field has been investigated systematically. By successive elimination of a number of disturbing factors an experimental procedure has been developed which yields consistent and reproducible results. The metals lead, mercury and tin have been investigated in this manner. Contrary to the accepted view it has been found that under ‘ideal’ conditions the transition is not discontinuous. There exists a range of temperature and magnetic field in which the resistance changes gradually from normal to zero and vice versa. The extent of this transition region was found to grow' rapidly with increasing absolute value of the magnetic field. Under conditions closely approximating the ‘ideal’ longitudinal case transitions with hysteresis were never observed. However, it could be shown that resistance hysteresis and discontinuous resistive changes are produced by deviation from the longitudinal case owing to unsuitable geometrical shape of the specimen. The general conclusion has therefore been reached that the resistance of a pure superconductor in a longitudinal field changes continuously in transition between the superconductive and the normal state. The significance of the results has been discussed and further experiments have been proposed.

scholarly journals Protostellar birth with ambipolar and ohmic diffusion

2018 ◽  
Vol 615 ◽  
pp. A5 ◽  
Author(s):  
N. Vaytet ◽  
B. Commerçon ◽  
J. Masson ◽  
M. González ◽  
G. Chabrier
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Adaptive Mesh Refinement ◽  
Protoplanetary Disks ◽  
Adaptive Mesh ◽  
Magnetic Diffusion ◽  
Ideal Mhd ◽  
The Impact ◽  
The Magnetic Field ◽  
The Ideal

Context. The transport of angular momentum is fundamental during the formation of low-mass stars; too little removal and rotation ensures stellar densities are never reached, too much and the absence of rotation means no protoplanetary disks can form. Magnetic diffusion is seen as a pathway to resolving this long-standing problem. Aims. We aim to investigate the impact of including resistive magnetohydrodynamics (MHD) in simulations of the gravitational collapse of a 1 M⊙ gas sphere, from molecular cloud densities to the formation of the protostellar seed; the second Larson core. Methods. We used the adaptive mesh refinement code RAMSES to perform two 3D simulations of collapsing magnetised gas spheres, including self-gravity, radiative transfer in the form of flux-limited diffusion, and a non-ideal gas equation of state to describe H2 dissociation which leads to the second collapse. The first run was carried out under the ideal MHD approximation, while ambipolar and ohmic diffusion was incorporated in the second calculation using resistivities computed from an equilibrium chemical network. Results. In the ideal MHD simulation, the magnetic field dominates the energy budget everywhere inside and around the first hydrostatic core, fueling interchange instabilities and driving a low-velocity outflow above and below the equatorial plane of the system. High magnetic braking removes essentially all angular momentum from the second core. On the other hand, ambipolar and ohmic diffusion create a barrier which prevents amplification of the magnetic field beyond 0.1 G in the first Larson core which is now fully thermally supported. A significant amount of rotation is preserved and a small Keplerian-like disk forms around the second core. The ambipolar and ohmic diffusions are effective at radii below 10 AU, indicating that a least ~1 AU is necessary to investigate the angular momentum transfer and the formation of rotationally supported disks. Finally, when studying the radiative efficiency of the first and second core accretion shocks, we found that it can vary by several orders of magnitude over the 3D surface of the cores. Conclusions. This proves that magnetic diffusion is a prerequisite to star formation. Not only does it enable the formation of protoplanetary disks in which planets will eventually form, it also plays a determinant role in the formation of the protostar itself.

Nonlinear stability of axisymmetric ideal magnetohydrodynamic flows

2003 ◽  
Vol 69 (4) ◽  
pp. 339-362 ◽  
Author(s):  
A. H. KHATER ◽  
D. K. CALLEBAUT ◽  
S. M. MOAWAD
Keyword(s):  
Magnetic Field ◽  
General Theory ◽  
Arbitrary Field ◽  
Mean Square ◽  
Magnetohydrodynamic Flows ◽  
Fixed Axis ◽  
The Mean ◽  
Ideal Magnetohydrodynamic ◽  
The Magnetic Field ◽  
The Ideal

In this paper the general theory developed by Vladimirov et al. is extended to nonlinear (Lyapunov) stability for axisymmetric (invariant under rotations around a fixed axis) solutions of the ideal incompressible magnetohydrodynamic flows for a particular situation, namely arbitrary field and poloidal flow. The appropriate norm is a sum of magnetic and kinetic energies and the mean square vector potential of the magnetic field.

Investigation of the localized co-interchange instabilities in a rotamak plasma

1989 ◽  
Vol 41 (3) ◽  
pp. 517-522
Author(s):  
W. K. Bertram
Keyword(s):  
Magnetic Field ◽  
Stability Criterion ◽  
Vortex Point ◽  
Ohm’S Law ◽  
Ideal Mhd ◽  
Ohm's Law ◽  
The Magnetic Field ◽  
The Ideal

If the rotamak is regarded as a spherical field-reversed mirror then, according to conventional ideal MHD analysis, it should be unstable to co-interchange modes localized near the vortex point of the magnetic field. It is shown that to study these instabilities in a typical rotamak plasma, the Hall term in Ohm's law cannot be ignored. The effect of the Hall term on the ideal MHD analysis of co-interchange modes is investigated and a stability criterion is derived.

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