Magneto-acoustic Waves through an Electrically Conducting Medium in the Presence of a Magnetic Field

1964 ◽  
Vol 15 (3) ◽  
pp. 173-175
Author(s):  
Yoshihito TAKESADA
Keyword(s):  
Magnetic Field ◽  
Acoustic Waves ◽  
Conducting Medium ◽  
Electrically Conducting

The slow motion of a magnetized sphere in a conducting medium

1960 ◽  
Vol 8 (2) ◽  
pp. 307-314 ◽  
Author(s):  
James R. Barthel ◽  
Paul S. Lykoudis
Keyword(s):  
Magnetic Field ◽  
Slow Motion ◽  
Conducting Medium ◽  
Total Drag ◽  
Electrically Conducting ◽  
Magnetic Forces ◽  
Pressure Fields ◽  
Viscous Pressure ◽  
Magnetic Poles ◽  
The Magnetic Field

This paper considers the slow motion of a sphere, permanently and uniformly magnetized in one direction, in a viscous electrically conducting medium. The line of the magnetic poles is assumed to be parallel to the direction of the motion of the sphere. The velocity and pressure fields are calculated by two iterations. The distortion of the magnetic field is also calculated. An expression is obtained for total drag due to the viscous, pressure and magnetic forces.

The decay of perturbations in an electrically conducting and thermally radiating gas

1973 ◽  
Vol 60 (1) ◽  
pp. 63-79 ◽  
Author(s):  
M. Srinivasa Sarma ◽  
L. V. K. V. Sarma
Keyword(s):  
Magnetic Field ◽  
Acoustic Waves ◽  
Constant Pressure ◽  
Initial Step ◽  
Temperature Perturbation ◽  
Constant Density ◽  
Cooling Process ◽  
Electrically Conducting ◽  
Pressure Perturbations ◽  
The Magnetic Field

The decay of perturbations in an infinite, thermally radiating gas of perfect electrical conductivity in the presence of magnetic field is studied. Complete solutions for the decay of initial sinusoidal perturbations in the temperature, gas velocity and pressure are determined. The sinusoidal perturbations are superposed to yield solutions for the decay of initial ‘step’ temperature profiles consisting of a constant initial temperature perturbation inside a finite planar region, with zero temperature perturbation outside. For a broad range of small and intermediate Boltzmann numbers the cooling proceeds in time from being a constant-density cooling process to being a constant-pressure cooling process. The magnetic field causes slower temperature decay with time and makes the temperature perturbations tend to attain constant-pressure cooling values. It quickens the decay of velocity and pressure perturbations and thus the transition from a constant-density to a constant-pressure cooling process is hastened. This transition is produced by the magneto-acoustic waves generated near the profile edges by the radiative cooling.

scholarly journals Possible Hydromagnetic Simulation of Cosmical Phenomena in the Laboratory

1958 ◽  
Vol 8 ◽  
pp. 1090-1094
Author(s):  
Winston H. Bostick
Keyword(s):  
Magnetic Field ◽  
Magnetic Reynolds Number ◽  
Electric Resistivity ◽  
Conducting Medium ◽  
Ionized Gas ◽  
Plasma Gun ◽  
Electrically Conducting ◽  
Magnetic Forces ◽  
Gas Plasma ◽  
The Magnetic Field

A technique has been developed whereby ionized gas (plasma) can be projected, by magnetic forces, at speeds of 3X107 cm/sec through a vacuum region free from a magnetic field. The plasma has also been projected across magnetic fields in vacuum at speeds of 107 cm/sec. It is further possible to have present in the magnetic field a background electrically conducting medium in the form of a low-pressure (about one micron) ionized gas. This gas is photoionized by the ultraviolet light from the plasma gun. With the background conducting medium we can calculate, following Spitzer, the electric resistivity η transverse to a strong magnetic field to be η = 1.29X1013(Z lnΛ)T−3/2 emu = 106 emu for T=105 °K (electron temperature), Z=1, lnΛ = 2.3. The magnetic Reynolds number Rm for L =10 cm and V = 107 cm/sec is thus Rm=4πLV/η = 103. Consequently, there is no doubt that with this technique we are producing magnetohydrodynamic phenomena in the laboratory.

scholarly journals 46. The störmertron

1958 ◽  
Vol 6 ◽  
pp. 446-447
Author(s):  
Willard H. Bennett
Keyword(s):  
Magnetic Field ◽  
Charged Particles ◽  
Mercury Vapor ◽  
Electron Gun ◽  
Conducting Film ◽  
New Developments ◽  
Electrically Conducting ◽  
The Earth ◽  
Magnetic Dipole Field ◽  
Glass Tubes

A tube has been developed in which the shapes of streams of charged particles moving in the earth's magnetic field can be produced accurately to scale. The tube has been named the Störmertron in honor of Carl Störmer who calculated many such orbits. New developments which have made this tube possible include a method for coating the inside of large glass tubes with a transparent electrically conducting film, and an electron gun producing gas-focused streams in less than ½ micron of mercury vapor, a nearly vapor-free grease joint, and a nearly vapor-free carbon black. The magnetic dipole field of the earth is simulated with an Alnico magnet capped with properly shaped soft iron caps. The stream is deflected using two pairs of yoke coils near the gun.

Transverse surface waves in magneto-elasticity

1966 ◽  
Vol 62 (3) ◽  
pp. 541-545 ◽  
Author(s):  
C. M. Purushothama
Keyword(s):  
Magnetic Field ◽  
Wave Propagation ◽  
Surface Waves ◽  
Elastic Medium ◽  
Uniform Magnetic Field ◽  
Shear Waves ◽  
Plane Shear ◽  
Electrically Conducting ◽  
Velocity Of Propagation

AbstractIt has been shown that uncoupled surface waves of SH type can be propagated without any dispersion in an electrically conducting semi-infinite elastic medium provided a uniform magnetic field acts non-aligned to the direction of wave propagation. In general, the velocity of propagation will be slightly greater than that of plane shear waves in the medium.

Parametric excitation of magnetoacoustic waves by a pump magnetic field in a high-β plasma

1977 ◽  
Vol 17 (1) ◽  
pp. 93-103 ◽  
Author(s):  
N. F. Cramer
Keyword(s):  
Magnetic Field ◽  
Parametric Excitation ◽  
Acoustic Waves ◽  
Magnetic Pressure ◽  
Gas Pressure ◽  
Alfven Wave ◽  
Fast Wave ◽  
Magnetoacoustic Waves ◽  
Background Magnetic Field ◽  
The Waves

The parametric excitation of slow, intermediate (Alfvén) and fast magneto-acoustic waves by a modulated spatially non-uniform magnetic field in a plasma with a finite ratio of gas pressure to magnetic pressure is considered. The waves are excited in pairs, either pairs of the same mode, or a pair of different modes. The growth rates of the instabilities are calculated and compared with the known result for the Alfvén wave in a zero gas pressure plasma. The only waves that are found not to be excited are the slow plus fast wave pair, and the intermediate plus slow or fast wave pair (unless the waves have a component of propagation direction perpendicular to both the background magnetic field and the direction of non-uniformity of the field).

Dynamics of nonlinear ion-acoustic waves in an external magnetic field

1985 ◽  
Vol 44 (8) ◽  
pp. 537-543 ◽  
Author(s):  
E. Infeld ◽  
P. Frycz ◽  
T. Czerwiśka-Lenkowska
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Acoustic Waves ◽  
Ion Acoustic Waves ◽  
Ion Acoustic
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