SCATTERING OF RADIO WAVES BY AN IONIZED GAS IN THERMAL EQUILIBRIUM IN THE PRESENCE OF A UNIFORM MAGNETIC FIELD

1961 ◽  
Vol 39 (5) ◽  
pp. 716-740 ◽  
Author(s):  
J. A. Fejer
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Thermal Equilibrium ◽  
Uniform Magnetic Field ◽  
Debye Length ◽  
Density Fluctuations ◽  
Total Power ◽  
Radio Waves ◽  
Ionized Gas ◽  
The Magnetic Field

In an earlier paper (Fejer 1960) a theory was developed for the scattering of radio waves by the electron density fluctuations that exist in an ionized gas in thermal equilibrium. The theory treated only the extreme cases where the "characteristic scale" of the scattering irregularities is either very much larger or very much smaller than the Debye length. The presence of only one type of singly charged ion was considered and the ion and electron temperatures were assumed equal. The effects of an external magnetic field were not taken into account.These earlier limitations are removed in the present paper and the effects of an external magnetic field are taken into account.It is shown that the total power is independent of the magnetic field and an expression for the frequency spectrum of scattered power in the presence of a uniform magnetic field is obtained. Useful approximations to this expression are derived for various limiting cases of interest.It is concluded that the magnetic field need not be taken into account in the interpretation of past observations by Bowles (1958, 1959) and by Pineo, Kraft, and Briscoe (1960). In future experiments, however, particularly at great heights, the effect of the magnetic field could be considerable.

SCATTERING OF RADIO WAVES BY AN IONIZED GAS IN THERMAL EQUILIBRIUM

1960 ◽  
Vol 38 (8) ◽  
pp. 1114-1133 ◽  
Author(s):  
J. A. Fejer
Keyword(s):  
Incident Wave ◽  
Thermal Equilibrium ◽  
Debye Length ◽  
Density Fluctuations ◽  
Characteristic Scale ◽  
Radio Waves ◽  
Ionized Gas ◽  
Positive Ions ◽  
Frequency Power Spectrum ◽  
Frequency Power

A theory is developed for the scattering of radio waves by density fluctuations which exist in an ionized gas in thermal equilibrium.Expressions for the frequency power spectrum of the scattered waves are obtained. These expressions make it possible to interpret the results of observations of this type of scattering from the ionosphere in terms of electron density and temperature.It is shown that if the characteristic scale of the scattering irregularities (this scale depends on the wavelength of the incident radio wave and the scattering angle) is much greater than the Debye length then the width of the spectrum of the scattered signal is determined by the thermal velocities (and the collision frequencies if the latter are sufficiently high) of the positive ions, rather than of the electrons.If the characteristic scale is greater than the Debye length then for low collision frequencies the spectrum is flat-topped, with two slightly raised shoulders situated symmetrically above and below the frequency of the incident wave. For high collision frequencies the spectrum has only one maximum situated at the frequency of the incident wave.

Characteristics of Ultrasound Propagation in a Magnetic Fluid Under Uniform Magnetic Field

2003 ◽  
Author(s):  
Masaaki Motozawa ◽  
Tatsuo Sawada
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetic Fluid ◽  
Uniform Magnetic Field ◽  
Colloidal Particles ◽  
Magnetic Field Intensity ◽  
Magnetic Field Direction ◽  
Ultrasound Propagation ◽  
Ultrasonic Propagation ◽  
The Magnetic Field

When an external magnetic field is applied to a magnetic fluid, some of the colloidal particles coagulate and form chain-like clusters. Properties of ultrasonic propagation wave are changed by these chain-like clusters. We carried out measurement of the ultrasonic propagation velocity in a magnetic fluid. Measurement were made by changing the magnetic field intensity from 0 mT to 570 mT, and the angle between the magnetic field direction and direction of the ultrasound propagation from 0° to 180°. The ultrasound frequencies were 1 MHz, 2 MHz and 4 MHz. Some of experimental results for the characteristics of ultrasound propagation in a magnetic fluid under a uniform magnetic field were reported.

scholarly journals Sum rules for an atomic hyperfine structure in a magnetic field

2006 ◽  
Vol 84 (9) ◽  
pp. 801-811
Author(s):  
Savely G Karshenboim
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Hyperfine Structure ◽  
Uniform Magnetic Field ◽  
Sum Rules ◽  
Magnetic Moments ◽  
Energy Levels ◽  
Linear Combinations ◽  
Nuclear Magnetic Moments ◽  
The Magnetic Field

The sum rules for the energy levels of a hyperfine multiplet in a constant uniform magnetic field are presented. It is found that for any value of the electron angular moment and the nuclear spin there are certain linear combinations of energy levels that do not depend on the magnetic field and can be used to determine the unperturbed hyperfine-structure separation in the presence of a perturbing magnetic field. It is also demonstrated that there are other linear combinations that are linear with the external magnetic field and hence can be used to determine bound values of the electron and nuclear magnetic moments. The accuracy of the approximation within which the result is valid is also discussed.PACS Nos.: 32.10.Fn, 32.60.+i1

scholarly journals A Rapid Magnetofluidic Micromixer Using Diluted Ferrofluid

2016 ◽  
Author(s):  
Majid Hejazian ◽  
Nam-Trung Nguyen
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
External Magnetic Field ◽  
Uniform Magnetic Field ◽  
Body Force ◽  
Low Cost ◽  
Magnetic Field Gradient ◽  
Mixing Efficiency ◽  
Biological Assays ◽  
The Magnetic Field

Effective and rapid mixing is essential for various chemical and biological assays. The present work reports a simple and low-cost micromixer based on magnetofluidic actuation. The device takes advantage of magnetoconvective secondary flow, a bulk flow induced by an external magnetic field, for mixing. A paramagnetic stream of diluted ferrofluid and a non-magnetic stream are introduced to a straight microchannel. A permanent magnet placed next to the microchannel induced a non-uniform magnetic field. The magnetic field gradient and the mismatch in magnetic susceptibility between the two streams create a body force, which leads to rapid and efficient mixing. The micromixer reported here could achieve a high throughput and a high mixing efficiency of 90 % in a relatively short microchannel.

The Effect of Magnetic Field on the Hydration of Nanoscopic Hydrophobic N-Alkane Plates

2011 ◽  
Vol 228-229 ◽  
pp. 1007-1011
Author(s):  
Wei Wei Zhang ◽  
Long Qiu Li ◽  
Guang Yu Zhang ◽  
Hui Juan Dong
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Dynamics Simulation ◽  
Free Energy Barrier ◽  
Confined Water ◽  
Magnetic Exposure ◽  
Hydrophobic Solutes ◽  
The Magnetic Field ◽  
Density Of Water ◽  
Induced Adsorption

The effect of an external magnetic field on the hydration behavior of nanoscopic n-octane plates has been extensively investigated using molecular dynamics simulation in an isothermal-isobaric ensemble. The solute plates with different intermolecular spacing have also been considered to examine the effect of the topology of hydrophobic plates on the adsorption behavior of confined water in the presence of an external magnetic field with an intensity ranging from 0.1T to 1 T. The results demonstrate that magnetic exposure decreases the density of water for the plates with intermolecular spacing of a0 = 4 and 5 Å. This suggests that the free energy barrier for evaporation can be lowered by the applied field, and the hydrophobic solutes consisting of condensed n-octane molecules are apt to aggregate in the aqueous solution. In contrast, the magnetic field improves the dissolution or wetting of solutes comprised of loosely packed n-octane plates of a0=7Å. A magnetic-field-induced adsorption-to-desorption translation, which is in agreement with the experimental results provided by Ozeki, has also been observed for the plates with intermolecular spacing of a0 = 6 Å.

The stability of viscous flow in a curved channel in the presence of a magnetic field

1961 ◽  
Vol 264 (1317) ◽  
pp. 155-164 ◽  
Keyword(s):  
Magnetic Field ◽  
Viscous Flow ◽  
Uniform Magnetic Field ◽  
Axial Direction ◽  
Electrical Conductor ◽  
Curved Channel ◽  
Coaxial Cylinders ◽  
Transverse Pressure ◽  
The Stability ◽  
The Magnetic Field

The stability of viscous flow between two coaxial cylinders maintained by a constant transverse pressure gradient is considered when the fluid is an electrical conductor and a uniform magnetic field is impressed in the axial direction. The problem is solved and the dependence of the critical number for the onset of instability on the strength of the magnetic field and the coefficient of electrical conductivity of the fluid is determined.

scholarly journals Solar Spike Suggests a More Active Sun

Eos ◽  
2019 ◽  
Vol 100 ◽  
Author(s):  
Nola Redd
Keyword(s):  
Magnetic Field ◽  
The Sun ◽  
Radio Waves ◽  
The Magnetic Field

Radio waves are providing a new way to probe the Sun and suggest that the magnetic field of its corona may be stronger than long thought.

scholarly journals Spin-1/2 Particles under the Influence of a Uniform Magnetic Field in the Interior Schwarzschild Solution

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 467
Author(s):  
Fayçal Hammad ◽  
Alexandre Landry ◽  
Parvaneh Sadeghi
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Total Mass ◽  
Uniform Magnetic Field ◽  
Energy Levels ◽  
Relativistic Wave Equation ◽  
Relativistic Wave ◽  
Schwarzschild Solution ◽  
Relativistic Regime ◽  
The Magnetic Field

The relativistic wave equation for spin-1/2 particles in the interior Schwarzschild solution in the presence of a uniform magnetic field is obtained. The fully relativistic regime is considered, and the energy levels occupied by the particles are derived as functions of the magnetic field, the radius of the massive sphere and the total mass of the latter. As no assumption is made on the relative strengths of the particles’ interaction with the gravitational and magnetic fields, the relevance of our results to the physics of the interior of neutron stars, where both the gravitational and the magnetic fields are very intense, is discussed.

scholarly journals Radio Emission Model of a 'Typical' Pulsar

1987 ◽  
Vol 40 (6) ◽  
pp. 755 ◽  
Author(s):  
AZ Kazbegi ◽  
GZ Machabeli ◽  
G Melikidze
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Waves ◽  
Emission Model ◽  
Radio Waves ◽  
Resonance Case ◽  
Pulsar Magnetosphere ◽  
Pulsar Emission ◽  
Dipole Magnetic Field ◽  
New Type ◽  
The Magnetic Field

The generation of radio waves in the plasma of the pulsar magnetosphere is considered taking into account the inhomogeneity of the dipole magnetic field. It is shown that the growth rate of the instability of the electromagnetic waves calculated in the non-resonance case turns out to be of the order of 1/ TO (where TO is the time of plasma escape from the light cylinder). However, the generation of electromagnetic waves from a new type Cherenkov resonance is possible, occurring when the particles have transverse velocities caused by the drift due to the inhomogeneity of the magnetic field. Estimates show that the development of this type of instability is possible only for pulsars with ages which exceed 104 yr. We make an attempt to explain some peculiarities of 'typical' pulsar emission on the basis of the model developed.

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