Field Strength Parameter Research Articles

An approximate method for magnetic boundary layers

An approximate method is derived for obtaining the flow in magnetic boundary layers with aligned fields which were discussed by Stewartson (1965). On comparing with exact, computed solutions the method is found to be accurate when applied to forward stagnation point flow for the whole, allowable range of the magnetic field strength parameter. It is then applied to the layer that develops from the forward stagnation point on a circular cylinder placed in a uniform stream and values obtained for the point at which it separates from the surface.

Wannier-Stark ladders and the energy spectrum of an electron in a finite one dimensional crystal

The one-band hamiltonian for an electron in an open finite tight-binding chain in a uniform external electric field is exactly diagonalized. The exact energy eigenvector components are given in terms of the Lommel polynomials and the energy spectrum, for a chain of N atoms, corresponds to the zeros of the Lommel polynomial of degree N. From this general eigenvalue problem solution, limiting cases of the model are investigated. In the infinite N limit, with fixed field strength and hopping parameter, for all eigenvalues bounded with respect to the centre of the spectrum, the components of the eigenvectors converge to Bessel functions whose order is determined by the energy. An asymptotic analysis shows that these bounded eigenvalues converge quite rapidly to a Wannier-Stark ladder when N to infinity . The results can be applied to the study of certain new one-dimensional solids.

Eddy currents in an infinitely finely segmented Hall generator

The eddy currents in the cross-sectional plane of a conducting side wall Hall generator are studied. Fluid velocity and temperature effects are investigated by assuming two different types of flow, i.e., fully developed laminar flow and turbulent boundary-layer flow. The working fluid is a seeded combustion gas where the compositions were calculated by assuming chemical equilibrium. The electrical conductivity and Hall parameter are allowed to vary as functions of temperature and pressure, and their values are calculated based on approximations formulated by Frost. Cold and hot channel wall conditions reveal quite different current distributions under laminar, fully developed flow conditions, with the cold wall distribution being much more nonuniform. Under turbulent boundary-layer flow conditions, however, cold and hot wall current distributions exhibit relatively minor differences, with both cases approaching the limiting case of constant velocity and electrical properties. Increasing the magnetic field strength and Hall parameter tends to increase the nonuniformity of the current distribution. The power output of the Hall generator is shown to depend strongly on the wall temperature under laminar, fully developed flow conditions, but this dependence is greatly reduced when the turbulent boundary-layer velocity profile is assumed.

Neutrino Bremsstrahlung in an Intense Magnetic Field

In this paper we present the neutrino luminosity due to a completely relativistic electron gas in the presence of an intense magnetic field. The neutrino emission rate is determined rigorously, under the assumption of the $V\ensuremath{-}A$ theory of universal weak Fermi interaction, by standard field-theoretical methods. It is shown that the neutrino radiation rate can be expressed as a function of temperature, density, and the field-strength parameter $\ensuremath{\Theta}=\frac{H}{{H}_{c}}$, where ${H}_{c}=\frac{{m}^{2}{c}^{3}}{e\ensuremath{\hbar}}=4.414\ifmmode\times\else\texttimes\fi{}{10}^{13}$ G. Comparisons are made with previous approximate results due to others, and the reasons for discrepancies are discussed.

Alternative‐Current Field‐Induced Forces and Their Biological Implications

Steady‐state, field‐induced forces on particles of microscopic size become significant at field strength values of the order of 100 v/cm. They include “pearl‐chain formation,” i.e. the alignment of particles in the direction of the imposed field, and the orientation of nonspherical particles. The time constant, which describes the speed of these phenomena, depends on field strength, and particle and other parameters. For pulsed fields, a lower level of applied average power can suffice to evoke the phenomena mentioned. Biological implications include the possibility of nonthermal effects of biological significance.

Radio Sources having Spectra with a Low Frequency Cut-off

The four mechanisms that can be responsible for a cut-off in the spectrum of the radio frequency radiation from radio sources have been examined. The results of this analysis have been applied to fourteen sources in the 3C list, whose spectra have been shown to be curved by recent observations at 38 Mc/s. Useful limits are derived for the field strength and other parameters of these sources.

Ion-Focusing Properties of a Three-Element Quadrupole Lens System

The focusing properties of a three-element quadrupole lens system have been studied, and the results of thicklens calculations are presented in the form of graphs showing the field-strength parameters and magnifications, as functions of object and image distances.

Ion Focusing Properties of a Quadrupole Lens Pair

The focusing properties of a quadrupole lens pair have been studied, and the results of thick-lens calculations are presented in the form of graphs showing the field strength parameters and magnifications as functions of object and image distances.

On the hall effect in bismuth

We have applied the results of a previous paper to evaluate the Hall coefficient of bismuth at liquid helium temperatures, using a generalisation of Dingle's expression for the Fermi level as a function of the magnetic field strength and Shoenberg's parameters for the energy surfaces. The oscillatory part of the Hall coefficient is satisfactorily reproduced, but our theory predicts a linear behaviour of the non-oscillatory part, while a quadratic dependence is found experimentally. Including the contribution to the conductivity due to holes changes the field dependence of the steady part of the Hall coefficient from H to H1.3, and does not significantly alter the absolute magnitude or the oscillatory part.