scholarly journals Proof-of-principle demonstration of a translating coils-based method for measuring the magnetic field of axially-symmetric magnets

2015 ◽  
Vol 10 (02) ◽  
pp. P02004-P02004 ◽  
Author(s):  
P. Arpaia ◽  
M. Buzio ◽  
M. Kazazi ◽  
S. Russenschuck
Keyword(s):  
Magnetic Field ◽  
Axially Symmetric ◽  
The Magnetic Field ◽  
Proof Of Principle

scholarly journals Two-fluid simulations of the magnetic field evolution in neutron star cores in the weak-coupling regime

2020 ◽  
Vol 498 (2) ◽  
pp. 3000-3012 ◽  
Author(s):  
F Castillo ◽  
A Reisenegger ◽  
J A Valdivia
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Charged Particles ◽  
Stable Stratification ◽  
Composition Gradient ◽  
Axially Symmetric ◽  
Drag Forces ◽  
Degeneracy Pressure ◽  
The Magnetic Field ◽  
Two Fluid

ABSTRACT In a previous paper, we reported simulations of the evolution of the magnetic field in neutron star (NS) cores through ambipolar diffusion, taking the neutrons as a motionless uniform background. However, in real NSs, neutrons are free to move, and a strong composition gradient leads to stable stratification (stability against convective motions) both of which might impact on the time-scales of evolution. Here, we address these issues by providing the first long-term two-fluid simulations of the evolution of an axially symmetric magnetic field in a neutron star core composed of neutrons, protons, and electrons with density and composition gradients. Again, we find that the magnetic field evolves towards barotropic ‘Grad–Shafranov equillibria’, in which the magnetic force is balanced by the degeneracy pressure gradient and gravitational force of the charged particles. However, the evolution is found to be faster than in the case of motionless neutrons, as the movement of charged particles (which are coupled to the magnetic field, but are also limited by the collisional drag forces exerted by neutrons) is less constrained, since neutrons are now allowed to move. The possible impact of non-axisymmetric instabilities on these equilibria, as well as beta decays, proton superconductivity, and neutron superfluidity, are left for future work.

scholarly journals High-energy collision of particles in the magnetic field far from black holes

2014 ◽  
Vol 29 (29) ◽  
pp. 1450151
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Center Of Mass ◽  
High Energy ◽  
Axially Symmetric ◽  
High Energy Collision ◽  
Mass Frame ◽  
Symmetric Black Hole ◽  
Rotating Star ◽  
The Magnetic Field

We consider collision of two particles in the axially symmetric black hole metric in the magnetic field. If the value of the angular momentum |L| of one particles grows unbound (but its Killing energy remains fixed) one can achieve unbound energy in the center-of-mass frame E c.m. In the absence of the magnetic field, collision of this kind is known to happen in the ergoregion. However, if the magnetic field strength B is also large, with the ratio |L|/B being finite, large E c.m. can be achieved even far from a black hole, in the almost flat region. Such an effect also occurs in the metric of a rotating star.

scholarly journals Proof of Principle of a Rotating Actuator Based on Magnetostrictive Material with Simultaneous Vibration Amplitude

Actuators ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 81 ◽  
Author(s):  
Christian Titsch ◽  
Qiang Li ◽  
Simon Kimme ◽  
Welf-Guntram Drossel
Keyword(s):  
Magnetic Field ◽  
Smart Materials ◽  
Vibration Amplitude ◽  
Piezoelectric Materials ◽  
Longitudinal Direction ◽  
Ultrasonic Machining ◽  
Ultrasonic Assisted ◽  
Ultrasonic Assisted Machining ◽  
The Magnetic Field ◽  
Proof Of Principle

Magnetostrictive materials are a group of smart materials with comparable properties to piezoelectric materials regarding strain and operating frequency. In contrast, the Curie temperature is much higher and the principle effect allows different actuator designs. Especially in the case of rotating actuators in ultrasonic assisted machining, a high potential is seen for a simplified energy transmission. In the study, a test stand for a rotating actuator with simultaneous vibration in longitudinal direction was designed to show the proof of principle for this idea. It was shown that the current inducing the magnetic field as well as its frequency influence the amplitude of the rotating actuator. This is a first step to developing a rotating actuator for ultrasonic machining.

Gravitationsinstabilitäten eines Plasmas bei differentieller Rotation

1967 ◽  
Vol 22 (4) ◽  
pp. 431-437
Author(s):  
R. Ebert
Keyword(s):  
Magnetic Field ◽  
Differential Rotation ◽  
Wave Length ◽  
Critical Value ◽  
Unstable Wave ◽  
Simultaneous Action ◽  
Axially Symmetric ◽  
Gas Density ◽  
Axis Of Rotation ◽  
The Magnetic Field

In this paper an instability calculation is given for an axially symmetric gas distribution which has a differential rotation and in which a magnetic field is present. It is a generalization of similar calculations given by CHANDRASEKHAR and BEL and SCHATZMAN. The generalization becomes necessary for the study of problems of the formation of planetary systems, and star formation.The instability conditions and the critical wave lengths are calculated for plane-wave-like disturbances. For disturbances running perpendicularly to the axis of rotation instability can occur only if the gas density exceeds a critical value which depends on the differential rotation at the considered distance only as long as pressure gradients and gradients of the magnetic field strength are negligible. If the gas density exceeds this critical value the shortest unstable wave length is proportional to the square root of vT2+vB2, where vT means the velocity of sound and vB the ALFVÉN-velocity.For disturbances running parallel to the axis of rotation in addition to the JEANS instability a new type of instability occurs due to the simultaneous action of the magnetic field and the differential rotation; for rigid rotation this instability vanishes.

scholarly journals Charged Particle Motion in a Time?Dependent Axially Symmetric Magnetic Field

1965 ◽  
Vol 18 (6) ◽  
pp. 553 ◽  
Author(s):  
PW Seymour ◽  
RB Leipnik ◽  
AF Nicholson
Keyword(s):  
Magnetic Field ◽  
Charged Particle ◽  
Constant Velocity ◽  
Short Review ◽  
Time Dependent ◽  
Radial Compression ◽  
Axially Symmetric ◽  
Cylindrical Coordinates ◽  
Drift Theory ◽  
The Magnetic Field

Following a short review of the drift theory of plasma radial compression, an exact solution for the motion of a charged particle in an axially symmetric time-dependent magnetic field is� obtained. The method gives forms for the cylindrical coordinates rand B of the charged particle that have a simple interpretation, the z-motion being of constant velocity. As examples, the exact results are discussed for a simple power law and an exponential time dependence of the magnetic field and, using the latter results, the drift theory of plasma radial compression is qualitatively verified.

scholarly journals Caputo-Fabrizio Time Fractional Derivative Applied to Visco Elastic MHD Fluid Flow in the Porous Medium

2018 ◽  
Vol 7 (4.30) ◽  
pp. 533
Author(s):  
Salah Uddin ◽  
M. Mohamad ◽  
M. A. H. Mohamad ◽  
Suliadi Sufahani ◽  
M. Ghazali Kamardan ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Fluid Flow ◽  
Fractional Derivative ◽  
Fractional Derivatives ◽  
Hartmann Number ◽  
Fluid Velocity ◽  
Axially Symmetric ◽  
Governing Equations ◽  
Permeability Parameter ◽  
The Magnetic Field

In this paper the laminar fluid flow in the axially symmetric porous cylindrical channel subjected to the magnetic field was studied. Fluidmodel was non-Newtonian and visco elastic. The effects of magnetic field and pressure gradient on the fluid velocity were studied by using a new trend of fractional derivative without singular kernel. The governing equations consisted of fractional partial differential equations based on the Caputo-Fabrizio new time-fractional derivatives NFDt. Velocity profiles for various fractional parameter a, Hartmann number, permeability parameter and elasticity were reported. The fluid velocity inside the cylindrical artery decreased with respect to Hartmann number, permeability parameter and elasticity. The results obtained from the fractional derivative model are significantly different from those of the ordinary model.  

scholarly journals One component regularity criteria for the axially symmetric MHD-Boussinesq system

2021 ◽  
Vol 0 (0) ◽  
pp. 0
Author(s):  
Zijin Li ◽  
Xinghong Pan
Keyword(s):  
Magnetic Field ◽  
Blow Up ◽  
A Priori ◽  
Strong Solutions ◽  
Boussinesq System ◽  
Regularity Criteria ◽  
Axially Symmetric ◽  
Magnetic Resistivity ◽  
Boussinesq Systems ◽  
The Magnetic Field

<p style='text-indent:20px;'>In this paper, we consider regularity criteria of a class of 3D axially symmetric MHD-Boussinesq systems without magnetic resistivity or thermal diffusivity. Under some Prodi-Serrin type critical assumptions on the horizontal angular component of the velocity, we will prove that strong solutions of the axially symmetric MHD-Boussinesq system can be smoothly extended beyond the possible blow-up time <inline-formula><tex-math id="M1">\begin{document}$ T_\ast $\end{document}</tex-math></inline-formula> if the magnetic field contains only the horizontal swirl component. No a priori assumption on the magnetic field or the temperature fluctuation is imposed.</p>

scholarly journals (Self-)Magnetized Bose–Einstein condensate stars

2019 ◽  
Vol 28 (10) ◽  
pp. 1950135 ◽  
Author(s):  
G. Quintero Angulo ◽  
A. Pérez Martínez ◽  
H. Pérez Rojas ◽  
D. Manreza Paret
Keyword(s):  
Magnetic Field ◽  
Thermodynamic Description ◽  
Compact Object ◽  
Einstein Condensate ◽  
Compact Objects ◽  
Magnetic Field Effects ◽  
Axially Symmetric ◽  
Bose Einstein Condensate ◽  
Bose Einstein ◽  
The Magnetic Field

We study magnetic field effects on the Equations-of-State (EoS) and the structure of Bose–Einstein Condensate (BEC) stars, i.e. a compact object composed by a gas of interacting spin-one bosons formed up by the pairing of two neutrons. To include the magnetic field in the thermodynamic description, we assume that particle–magnetic field and particle–particle interactions are independent. We consider two configurations for the magnetic field: one where it is constant and externally fixed, and another where it is produced by the bosons through self-magnetization. Stable configurations of self-magnetized and magnetized nonspherical BEC stars are studied using structure equations that describe axially symmetric objects. In general, the magnetized BEC stars are spheroidal, less massive and smaller than the nonmagnetic ones, being these effects more relevant at low densities. Nevertheless, star masses around two solar masses are obtained by increasing the strength of the boson–boson interaction. The inner magnetic field profiles of the self-magnetized BEC stars can be computed as a function of the equatorial radii. The values obtained for the core and surface magnetic fields are in agreement with those typically found in compact objects.

On the Motion of a Charged Particle in an Axially Symmetric Magnetic Field

1971 ◽  
Vol 26 (12) ◽  
pp. 2068-2070
Author(s):  
V. L. Bharadwaj
Keyword(s):  
Magnetic Field ◽  
Charged Particle ◽  
Configuration Space ◽  
Plasma Stream ◽  
Axially Symmetric ◽  
Interaction Forces ◽  
Transverse Pressure ◽  
Steady Current ◽  
Test Charge ◽  
The Magnetic Field

The object of this note is to study the motion of a charged particle entering the magnetic field due to a steady current inside a plasma column. Even if the particles of the plasmas stream mutually interact, their distribution across the stream can be such that the interaction forces are balanced by the transverse pressure gradient in the plasma 1. It is shown here that the test charge entering the plasma stream remains bounded to the stream between two coaxial cylindrical surfaces and further that under suitable conditions it may remain trapped inside a cylindrical box. FISSER and KIPPENHAHN 2 have discussed the general problem of the motion of a charged particle in an axially symmetric magnetic field in configuration space. The following is a particular case of that problem. HERTWECK 3 has investigated the motion of a test charge in the magnetic field due to a line current. His results are applicable here if the test charge remains outside the plasma stream

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