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.

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.

scholarly journals Connecting magnetic fields from sub-galactic scale to clusters of galaxies and beyond with cosmological MHD simulations

2015 ◽  
Vol 11 (A29B) ◽  
pp. 699-699
Author(s):  
Klaus Dolag ◽  
Alexander M. Beck ◽  
Alexander Arth
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Heat Transport ◽  
Galaxy Clusters ◽  
Large Scale ◽  
High Redshift ◽  
Galactic Halos ◽  
Rotation Measure ◽  
The Magnetic Field ◽  
Good Agreement

AbstractUsing the MHD version of Gadget3 (Stasyszyn, Dolag & Beck 2013) and a model for the seeding of magnetic fields by supernovae (SN), we performed simulations of the evolution of the magnetic fields in galaxy clusters and study their effects on the heat transport within the intra cluster medium (ICM). This mechanism – where SN explosions during the assembly of galaxies provide magnetic seed fields – has been shown to reproduce the magnetic field in Milky Way-like galactic halos (Beck et al. 2013). The build up of the magnetic field at redshifts before z = 5 and the accordingly predicted rotation measure evolution are also in good agreement with current observations. Such magnetic fields present at high redshift are then transported out of the forming protogalaxies into the large-scale structure and pollute the ICM (in a similar fashion to metals transport). Here, complex velocity patterns, driven by the formation process of cosmic structures are further amplifying and distributing the magnetic fields. In galaxy clusters, the magnetic fields therefore get amplified to the observed μG level and produce the observed amplitude of rotation measures of several hundreds of rad/m2. We also demonstrate that heat conduction in such turbulent fields on average is equivalent to a suppression factor around 1/20th of the classical Spitzer value and in contrast to classical, isotropic heat transport leads to temperature structures within the ICM compatible with observations (Arth et al. 2014).

A time‐domain EM system measuring the step response of the ground

Geophysics ◽  
1984 ◽  
Vol 49 (7) ◽  
pp. 1010-1026 ◽  
Author(s):  
G. F. West ◽  
J. C. Macnae ◽  
Y. Lamontagne
Keyword(s):  
Magnetic Fields ◽  
Impulse Response ◽  
Electric Fields ◽  
Time Domain ◽  
Wide Band ◽  
Step Response ◽  
System Function ◽  
Response Measurement ◽  
Resistivity Method ◽  
Electric And Magnetic Fields

A wide‐band time‐domain EM system, known as UTEM, which uses a large fixed transmitter and a moving receiver has been developed and used extensively in a variety of geologic environments. The essential characteristics that distinguish it from other systems are that its system function closely approximates a stepfunction response measurement and that it can measure both electric and magnetic fields. Measurement of step rather than impulse response simplifies interpretation of data amplitudes, and improves the detection of good conductors in the presence of poorer ones. Measurement of electric fields provides information about lateral conductivity contrasts somewhat similar to that obtained by the gradient array resistivity method.

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.

Hall Currents and the Ejection of Prominences by Sunspots

1949 ◽  
Vol 2 (1) ◽  
pp. 39
Author(s):  
RG Giovanelli
Keyword(s):  
Magnetic Fields ◽  
Electric Fields ◽  
Magnetic Force ◽  
Large Space ◽  
Space Charges ◽  
Surrounding Atmosphere ◽  
Electric And Magnetic Fields ◽  
Order Of Magnitude ◽  
General Movement ◽  
Set Up

During the growth of sunspots induced electric fields may be expected to be set up in the surrounding atmosphere. It is shown that, because of the comparatively low conductivity perpendicular to lines of magnetic force, there are localized regions where large space charges occur, resulting in large electric fields perpendicular to the lines of magnetic force. Consequently both positive and negative charges drift in the same sense in a direction which is at right angles to the electric and magnetic fields, giving rise to a general movement of the gas. The drift velocities are difficult to estimate, but appear to be of the order of magnitude of those found in eruptive prominences.

scholarly journals Влияние магнитных и электрических полей на динамику образования плазмоидов в гатчинском разряде

2022 ◽  
Vol 92 (3) ◽  
pp. 366
Author(s):  
Shixin Zhao ◽  
Chengxun Yuan ◽  
А.А. Кудрявцев ◽  
Jingfeng Yao ◽  
Г.Д. Шабанов
Keyword(s):  
Magnetic Fields ◽  
Electric Fields ◽  
Electric Charge ◽  
Active Phase ◽  
Ball Lightning ◽  
Electric And Magnetic Fields ◽  
Direction Of Movement

The behavior in magnetic and electric fields of the Gatchina discharge, which is used mainly to create an analog of ball lightning in the laboratory in a normal atmosphere, is analyzed. Shown that in these studies it is possible to determine the sign of an uncompensated electric charge as in the active phase of the discharge, and in the forming long-lived luminous formations. Also shown that electric and magnetic fields can change the direction of movement of the forming luminous formation and even completely block its formation. The type and mechanism of existence firework ball lightning are considered, photos of which are presented in widely known monographs on the ball lightning.

Reply to J. R. Wait by D. Rankin and R. P. Singh

Geophysics ◽  
1984 ◽  
Vol 49 (8) ◽  
pp. 1388-1388
Author(s):  
D. Rankin ◽  
R. P. Singh
Keyword(s):  
Magnetic Fields ◽  
Electric Fields ◽  
Horizontal Surface ◽  
Electric And Magnetic Fields ◽  
Surface Measurements

There is no real dispute between the magnetotellurist (Cagniard school) and the radio physicist (Norton school) in surface measurements of VLF and ULF fields. Each defines a mutually exclusive quantity which requires a different mode of measurement. The magnetotellurist measures the horizontal surface electric and magnetic fields, whereas, as Wait correctly points out, the radio physicist measures the horizontal and vertical electric fields.

Viscosity of a Polar Gas of Symmetric Top Molecules in Perpendicular Electric and Magnetic Fields

1978 ◽  
Vol 33 (2) ◽  
pp. 225-227 ◽  
Author(s):  
W. E. Köhler
Keyword(s):  
Magnetic Fields ◽  
Kinetic Theory ◽  
Electric Field ◽  
Electric Fields ◽  
Pressure Difference ◽  
Viscosity Coefficients ◽  
Electric And Magnetic Fields ◽  
Symmetric Top Molecules ◽  
Field Influence

A kinetic theory treatment of the influence of perpendicular magnetic and electric fields on the viscosity is given for a polar gas of symmetric top molecules. Expressions for the 9 independent viscosity coefficients are derived. In particular, the electric field influence on the transverse viscomagnetic pressure difference is studied.

Proton acceleration in three-dimensional non-null magnetic reconnection

2016 ◽  
Vol 82 (5) ◽  
Author(s):  
Z. Akbari ◽  
M. Hosseinpour ◽  
M. A. Mohammadi
Keyword(s):  
Magnetic Field ◽  
Energy Distribution ◽  
Magnetic Reconnection ◽  
Electric Fields ◽  
Three Dimensional ◽  
Null Point ◽  
Proton Acceleration ◽  
Electric And Magnetic Fields ◽  
Field Lines ◽  
The Magnetic Field

In a three-dimensional non-null magnetic reconnection, the process of magnetic reconnection takes place in the absence of a null point where the magnetic field vanishes. By randomly injecting a population of 10 000 protons, the trajectory and energy distribution of accelerated protons are investigated in the presence of magnetic and electric fields of a particular model of non-null magnetic reconnection with the typical parameters for the solar corona. The results show that protons are accelerated along the magnetic field lines away from the non-null point only at azimuthal angles where the magnitude of the electric field is strongest and therefore particles obtain kinetic energies of the order of thousands of MeV and even higher. Moreover, the energy distribution of the population depends strongly on the amplitude of the electric and magnetic fields. Comparison shows that a non-null magnetic reconnection is more efficient in accelerating protons to very high GeV energies than a null-point reconnection.

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