scholarly journals Approximate Formulas for Ion and Electron Transport Coefficients in Crossed Electric and Magnetic Fields

1994 ◽  
Vol 47 (3) ◽  
pp. 279 ◽  
Author(s):  
RE Robson
Keyword(s):  
Magnetic Fields ◽  
Transport Coefficients ◽  
Anisotropic Scattering ◽  
Negative Differential Conductivity ◽  
Differential Conductivity ◽  
Electric And Magnetic Fields ◽  
Electrons And Ions ◽  
Approximate Expressions ◽  
Electron Transport Coefficients ◽  
The Magnetic Field

Momentum-transfer theory is used to derive approximate expressions for transport properties of electrons and ions in a gas in crossed electric and magnetic fields. Included in the formal discussion are the generalised Einstein relations, negative differential conductivity, Tonks' theorem and the equivalent reduced electric field concept. Specific topics dealt with include the ratio D II / D1. for electrons, which 'flips over' as the magnetic field is increased, the enhancement of negative differential conductivity through increased BIN, and a discussion of anisotropic scattering.

scholarly journals Magnetotellurics with a remote magnetic reference

Geophysics ◽  
1979 ◽  
Vol 44 (1) ◽  
pp. 53-68 ◽  
Author(s):  
T. D. Gamble ◽  
W. M. Goubau ◽  
J. Clarke
Keyword(s):  
Magnetic Field ◽  
Standard Deviation ◽  
Magnetic Fields ◽  
Apparent Resistivity ◽  
The Other ◽  
Impedance Tensor ◽  
Free Data ◽  
Electric And Magnetic Fields ◽  
Conventional Methods ◽  
The Magnetic Field

Magnetotelluric measurements were performed simultaneously at two sites 4.8 km apart near Hollister, California. SQUID magnetometers were used to measure fluctuations in two orthogonal horizontal components of the magnetic field. The data obtained at each site were analyzed using the magnetic fields at the other site as a remote reference. In this technique, one multiplies the equations relating the Fourier components of the electric and magnetic fields by a component of magnetic field from the remote reference. By averaging the various crossproducts, estimates of the impedance tensor not biased by noise are obtained, provided there are no correlations between the noises in the remote channels and noises in the local channels. For some data, conventional methods of analysis yielded estimates of apparent resistivities that were biased by noise by as much as two orders of magnitude. Nevertheless, estimates of the apparent resistivity obtained from these same data, using the remote reference technique, were consistent with apparent resistivities calculated from relatively noise‐free data at adjacent periods. The estimated standard deviation for periods shorter than 3 sec was less than 5 percent, and for 87 percent of the data, was less than 2 percent. Where data bands overlapped between periods of 0.33 sec and 1 sec, the average discrepancy between the apparent resistivities was 1.8 percent.

Elastic Constants of Nematic Liquid Crystals

1972 ◽  
Vol 27 (6) ◽  
pp. 966-976 ◽  
Author(s):  
Hans Gruler ◽  
Terry J. Scheffer ◽  
Gerhard Meier
Keyword(s):  
Magnetic Fields ◽  
Electric Fields ◽  
Detailed Comparison ◽  
Theoretical Treatment ◽  
Electrical Capacitance ◽  
Normal Deformation ◽  
Electric And Magnetic Fields ◽  
The Magnetic Field ◽  
Dynamic Phenomena ◽  
Good Agreement

Abstract We present a theoretical treatment and give experimental observations of the deformation that occurs in a nematic liquid crystal when electric or magnetic fields are applied. We consider only normal deformations in the nematic material where fluid flow and other dynamic phenomena play no role. Three important sample geometries are considered in the magnetic field, and the experimentally observed deformations are in good agreement with theory. The normal deformation induced by electric fields is of interest from a device standpoint, and we give a solution for the deformation that is valid even for large dielectric anisotropics. This solution has been experimentally verified. We give a detailed comparison of the distortions produced by electric and magnetic fields and show that the deformations are of a similar form even though the field is nonuniform in the electric case. The change in birefringence and electrical capacitance as a function of distortion is discussed as a means of observing the deformation.

Movement of charge carriers in electric and magnetic fields

2020 ◽  
pp. 89-126
Author(s):  
Hermann Kolanoski ◽  
Norbert Wermes
Keyword(s):  
Magnetic Fields ◽  
Transport Equation ◽  
Approximate Solutions ◽  
Critical Energy ◽  
Charge Carriers ◽  
Einstein Relation ◽  
Boltzmann Transport ◽  
Electric And Magnetic Fields ◽  
Electrons And Ions ◽  
And Diffusion

For the detection of charged particles many detector principles exploit the ionisation in sensing layers and the collection of the generated charges by electrical fields on electrodes, from where the signals can be deduced. In gases and liquids the charge carriers are electrons and ions, in semiconductors they are electrons and holes. To describe the ordered and unordered movement of the charge carriers in electric and magnetic fields the Boltzmann transport equation is introduced and approximate solutions are derived. On the basis of the transport equation drift and diffusion are discussed, first in general and then for applications to gases and semiconductors. It turns out that, at least for the simple approximations, the treatment for both media is very similar, for example also for the description of the movement in magnetic fields (Lorentz angle and Hall effect) or of the critical energy (Nernst-Townsend-Einstein relation).

Suppression of runaway of electrons in a Lorentz plasma. II. crossed electric and magnetic fields

1970 ◽  
Vol 4 (3) ◽  
pp. 441-450 ◽  
Author(s):  
Barbara Abraham-Shrauner
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Electric Field ◽  
Electric Fields ◽  
Cyclotron Frequency ◽  
Collision Frequency ◽  
Uniform Electric Field ◽  
Drift Motion ◽  
Electric And Magnetic Fields ◽  
The Magnetic Field

Suppression of runaway of electrons in a weak, uniform electric field in a fully ionized Lorentz plasma by crossed magnetic and electric fields is analysed. A uniform, constant magnetic field parallel to a constant or harmonically time varying electric field does not alter runaway from that in the absence of the magnetic field. For crossed, constant fields the passage to runaway or to free motion as described by constant drift motion and spiral motion about the magnetic field is lengthened in time for strong magnetic fields. The new ‘runaway’ time scale is roughly the ratio of the cyclotron frequency to the collision frequency squared for cyclotron frequencies much greater than the collision frequency. All ‘runaway’ time scales may be given approximately by t2E Teff where tE is the characteristic time of the electric field and Teff is the ffective collision time as estimated from the appropriate component of the electrical conductivity.

INFLUENCE OF BOTH ELECTRIC AND MAGNETIC FIELDS ON THE POLARON IN A CYLINDRICAL QUANTUM DOT

2004 ◽  
Vol 18 (20n21) ◽  
pp. 2887-2899 ◽  
Author(s):  
RUI-QIANG WANG ◽  
HONG-JING XIE ◽  
YOU-BIN YU
Keyword(s):  
Magnetic Fields ◽  
Quantum Dot ◽  
Ground State Energy ◽  
Ground State ◽  
State Energy ◽  
Side Surface ◽  
Energy Shift ◽  
Longitudinal Optical ◽  
Electric And Magnetic Fields ◽  
The Magnetic Field

The polaronic correction to the ground-state energy of the electron confined in a cylindrical quantum dot (QD) subject to electric and magnetic fields along the growth axis has been investigated. Using a combinative approach of perturbative theory and variational wavefunction, calculations are performed for an infinitely deep confinement potential outside the QD within the effective mass and adiabatic approximation. We have treated the system by taking into consideration the interaction of the electron with the confined longitudinal optical (LO) phonons as well as the side surface (SSO) and the top surface (TSO) optical phonons.1,2 The ground-state energy shift is obtained as a function of the cylindrical radius and the strength of electric and magnetic fields. The results show that the magnetic field heavily enhances the three types of phonon mode contribution to the correction of the electron ground-state energy while the electric field only improves the contribution of surface phonons (SSO and TSO) but decreases the contribution of LO phonons.

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