Radiation from a magnetic line source in a moving isotropic plasma

1970 ◽  
Vol 48 (7) ◽  
pp. 873-878 ◽  
Author(s):  
T. Kojima ◽  
K. Itakura
Keyword(s):  
Radiation Pattern ◽  
Energy Flow ◽  
Velocity Vector ◽  
Poynting Vector ◽  
Position Vector ◽  
Magnetic Line ◽  
Isotropic Plasma ◽  
Radiation Problem ◽  
Radiated Energy ◽  
Special Case

The problem of radiation from an electric dipole placed in a moving isotropic plasma has been studied by Lee and Papas for a special case where the velocity of the plasma is relatively small compared with the light velocity in vacuum. In this paper, we consider a radiation problem for a more general case where no restriction is imposed on the magnitude of the velocity of the plasma, and for a case where the source of radiation is assumed to be a magnetic line source.We investigate theoretically the effects of the movement of the plasma on the far-zone radiated electromagnetic fields and on the radiation pattern. The results show that the Poynting vector has a circumferential component, and therefore the direction of radiated-energy flow deviates from the radial direction, and it depends on the magnitude of the velocity of the plasma and on the angle between the position vector of an observer and the velocity vector of the plasma. Some numerical examples of its deviation and of the radiation pattern are illustrated.

Investigation of energy conversion processes and wave activity related to dipolarization fronts observed by MMS

2021 ◽  
Author(s):  
Soboh Alqeeq ◽  
Olivier Le Contel ◽  
Patrick Canu ◽  
Alessandro Retino ◽  
Thomas Chust ◽  
...  
Keyword(s):  
Energy Conversion ◽  
Energy Flow ◽  
Poynting Vector ◽  
Wave Activity ◽  
Electromagnetic Energy ◽  
Particle Measurements ◽  
Dipolarization Front ◽  
The Earth ◽  
Current Densities ◽  
Scale Properties

<p>In the present work, we consider four dipolarization front (DF) events detected by MMS spacecraft in the Earth’s magnetotail during a substorm on 23rd of July 2017 between 16:05 and 17:19 UT. From their ion scale properties, we show that these four DF events embedded in fast Earthward plasma flows have classical signatures with increases of Bz, velocity and temperature and a decrease of density across the DF. We compute and compare current densities obtained from magnetic and particle measurements and analyse the Ohm’s law. Then we describe the wave activity related to these DFs. We investigate energy conversion processes via J.E calculations and estimate the importance of the electromagnetic energy flow by computing the divergence of the Poynting vector. Finally we discuss the electromagnetic energy conservation in the context of these DFs.</p>

scholarly journals A System for Acoustic Field Measurement Employing Cartesian Robot

2016 ◽  
Vol 23 (3) ◽  
pp. 333-343 ◽  
Author(s):  
Maciej Szczodrak ◽  
Adam Kurowski ◽  
Józef Kotus ◽  
Andrzej Czyżewski ◽  
Bożena Kostek
Keyword(s):  
Acoustic Field ◽  
Energy Flow ◽  
Velocity Vector ◽  
Sound Pressure ◽  
Sound Field ◽  
Acoustic Energy ◽  
The Other ◽  
Object Shape ◽  
Movement Path ◽  
Optimum Path

AbstractA system setup for measurements of acoustic field, together with the results of 3D visualisations of acoustic energy flow are presented in the paper. Spatial sampling of the field is performed by a Cartesian robot. Automatization of the measurement process is achieved with the use of a specialized control system. The method is based on measuring the sound pressure (scalar) and particle velocity(vector) quantities. The aim of the system is to collect data with a high precision and repeatability. The system is employed for measurements of acoustic energy flow in the proximity of an artificial head in an anechoic chamber. In the measurement setup an algorithm for generation of the probe movement path is included. The algorithm finds the optimum path of the robot movement, taking into account a given 3D object shape present in the measurement space. The results are presented for two cases, first without any obstacle and the other - with an artificial head in the sound field.

Enskog-Boltzmann-Equation for a Fluid of Nonspherical Particles

1982 ◽  
Vol 37 (7) ◽  
pp. 660-664
Author(s):  
H. Thurn ◽  
S. Hess
Keyword(s):  
Boltzmann Equation ◽  
Differential Cross Section ◽  
Cross Section ◽  
Differential Cross ◽  
Position Vector ◽  
Nonspherical Particles ◽  
Fixed Orientation ◽  
General Relations ◽  
The Impact ◽  
Special Case

Abstract The Enskog-Boltzmann-equation is generalized to fluids of nonsperical particles with fixed orientation, i.e. for overdamped rotational motion. General relations between the interparticle position vector at the instant of contact, the impact parameter and the differential cross section are derived. The dependence of these quantities of the orientations of the colliding particles is studied for the special case of hard ellipsoids.

scholarly journals Vortex energy flow in the tight focus of a non-vortex field with circular polarization

2020 ◽  
Vol 44 (1) ◽  
pp. 5-11
Author(s):  
V.V. Kotlyar ◽  
S.S. Stafeev ◽  
A.G. Nalimov
Keyword(s):  
Angular Momentum ◽  
Orbital Angular Momentum ◽  
Energy Flow ◽  
Poynting Vector ◽  
Focal Spot ◽  
Free Field ◽  
Longitudinal Component ◽  
Circularly Polarized ◽  
Linearly Polarized ◽  
Direct Energy

Using Richards-Wolf formulas, we show that an axisymmetric circularly polarized vortex-free field can be focused into a sharp subwavelength focal spot, around which there is a region where the light energy flow propagates along a spiral. This effect can be explained by the conversion of the spin angular momentum of the circularly polarized field into the orbital angular momentum near the focus, although the on-axis orbital angular momentum remains zero. It is also shown that a linearly polarized optical vortex with topological charge 2 forms near the focal plane an on-axis reverse energy flow (defined by the negative longitudinal component of the Poynting vector) whose amplitude is comparable with the direct energy flow.

Cherenkov radiation in spatially dispersive media

1981 ◽  
Vol 374 (1759) ◽  
pp. 531-541 ◽  
Keyword(s):  
Rest Frame ◽  
Fourier Integral ◽  
Dispersive Media ◽  
Relativistic Velocity ◽  
Isotropic Plasma ◽  
Exciton Transition ◽  
Circular Field ◽  
Longitudinal Plasma ◽  
Spatially Dispersive ◽  
Special Case

The Cherenkov fields of a proton, and a neutron, moving with a relativistic velocity in a spatially dispersive medium are studied in the rest frame of the particle. The model of the medium used is typical of the behaviour of a dielectric near an exciton transition, and includes as a special case a screening medium like an isotropic plasma. The Fourier integral for the field of a proton is shown to split up into three integrals, each of which is identical to that in an ordinary medium but for a weight factor dependent on the frequency of the Fourier component. Each of these integrals is associated with one mode of Cherenkov emission, with its own threshold. The motion of the charge gives rise to three coaxial diffuse circular field cones with an azimuthally symmetric intensity distribution. The output of photons in each mode is evaluated. The field and output of a relativistic neutron are also evaluated for different orientations of the magnetic moment of the neutron relative to the direction of motion. It is shown that there are only two cones in this case, consistent with the fact that magnetic sources cannot excite the longitudinal plasma mode in a medium which is spatially dispersive only in its electrical properties.

The Poynting vector field and the energy flow within a transformer

1986 ◽  
Vol 54 (6) ◽  
pp. 528-531 ◽  
Author(s):  
F. Herrmann ◽  
G. Bruno Schmid
Keyword(s):  
Vector Field ◽  
Energy Flow ◽  
Poynting Vector
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