Hysteresis and eddy-current losses of a transformer lamination viewed as an application of the Poynting theorem
Hysteresis and eddy current losses of transformer lamination as application of Poynting theorem
TRANSFORMER↗
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On the passage of radiation through inhomogeneous, moving media. XIV - Poynting's theorem revisited
Certain arguments by Ko and Chuang (1979) against Lerche's (1975) interpretation of Poynting's theorem for a moving medium with linear constitutive relations are rebutted. It is argued that the contentions of Ko and Chuang are misleading, at the very least, and devoid of original information. Ko and Chuang's ascription of the physical role played by various terms in Poynting's theorem are shown to be subjective and nonunique. It is concluded that the energy and momentum of an electromagnetic field can indeed be partitioned in an essentially arbitrary manner.
Lerche, I.↗
Modeling the electron cyclotron emission radiation signature from suprathermal electrons in a tokamak
An Electron Cyclotron Emission (ECE) modeling code has been developed to model ECE radiation with an arbitrary electron momentum distribution, a small oblique angle, both ordinary (O-mode) and extraordinary polarizations (X-mode), and multiple cyclotron frequency harmonics. The emission and absorption coefficients are calculated using the Poynting theorem from the cold plasma dispersion and the electron–microwave interaction from the full anti-Hermitian tensor. The modeling shows several ECE radiation signatures that can be used to diagnose the population of suprathermal electrons in a tokamak. First, in an n = 2 X-mode (X2) optically thick plasma and oblique ECE view, the modeling shows that only suprathermal electrons, which reside in a finite region of the velocity and space domains, can effectively generate cyclotron emissions to the ECE receiver. The code also finds that the O1 mode is sensitive to suprathermal electrons of both a high v ⊥ and v || , while the X2 mode is dominantly sensitive to suprathermal electrons of a high v ⊥ . Finally, the modeling shows that an oblique ECE system with both X/O polarization and a broad frequency coverage can be used to effectively yield information of the suprathermal electron population in a tokamak.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Conversion of Magnetic Energy to Plasma Kinetic Energy During Guide Field Magnetic Reconnection in the Laboratory
Here, we present laboratory measurements showing the two-dimensional (2D) structure of energy conversion during magnetic reconnection with a guide field over the electron and ion diffusion regions, resolving the separate energy deposition on electrons and ions. We find that the electrons are energized by the parallel electric field at two locations, at the X line and around the separatrices. On the other hand, the ions are energized ballistically by the perpendicular electric field in the vicinity of the high-density separatrices. An energy balance calculation by evaluating the terms of the Poynting theorem shows that 40% of the magnetic energy is converted to particle energy, 2/3 of which is transferred to ions and 1/3 to electrons. Further analysis suggests that the energy deposited on particles manifests mostly in the form of thermal kinetic energy in the diffusion regions.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
A Theoretical Investigation of the Input Characteristics of a Rectangular Cavity-Backed Slot Antenna
Equations which represent the magnetic and electric stored energies are derived for an infinite section of rectangular waveguide and a rectangular cavity. These representations which are referred to as being physically observable are obtained by considering the difference in the volume integrals appearing in the complex Poynting theorem. It is shown that the physically observable stored energies are determined by the field components that vanish in a reference plane outside the aperture. These physically observable representations are used to compute the input admittance of a rectangular cavity-backed slot antenna in which a single propagating wave is assumed to exist in the cavity. The slot is excited by a voltage source connected across its center; a sinusoidal distribution is assumed in the slot. Input-admittance calculations are compared with measured data. In addition, input-admittance curves as a function of electrical slot length are presented for several size cavities. For the rectangular cavity backed slot antenna, the quality factor and relative bandwidth were computed independently by using these energy relationships. It is shown that the asymptotic relationship which is usually assumed to exist between the quality bandwidth and the reciprocal of relative bandwidth is equally valid for the rectangular cavity backed slot antenna.
Cockrell, C. R.↗
A theoretical model for intense microwave pulse propagation in an air breakdown environment
A theoretical model based on two coupled partial differential equations is established to describe the propagation of an intense microwave pulse in air breakdown environment. One is derived from the Poynting theorem, and the other one is the rate equation of electron density. A semiempirical formula of the ionization frequency is adopted for this model. A transformation of these two equations to local time frame of reference is introduced so that they can be solved numerically with considerably reduced computation time.
Kuo, S. P.↗
Theoretical and experimental study of the input impedance of the cylindrical cavity-backed rectangular slot antennas
The authors study the input impedance of a cylindrical cavity-backed slot antenna based on mode matching and the complex Poynting theorem. Two cavity-backed slot antennas were fabricated to verify the theory. The numerical results agree very well with measurements. Two resonant frequencies were found from the input impedance. One resonant frequency is attributed to the rectangular slot and the other is due to the cavity. The slot length controls the first resonant frequency and has a much stronger effect on the input impedance at the antenna operating frequency as compared with the cavity length.
Li, Ming-Yi↗
Simulation of intense microwave pulse propagation in air breakdown environment
An experiment is conducted to examine the tail erosion phenomenon which occurs to an intense microwave pulse propagating in air breakdown environment. In the experiment, a 1 MW microwave pulse (1.1 microsec) is transmitted through a large plexiglas chamber filled with dry air at about 1-2 torr pressure. Two different degrees of tail erosion caused by two different mechanisms are identified. This experimental effort leads to the understanding of the fundamental behavior of tail erosion and provides a data base for validating the theoretical model. A theoretical model based on two coupled partial differential equations is established to describe the propagation on an intense microwave pulse in air breakdown environment. One is derived from the Poynting theorem, and the other one is the rate equation of electron density. A semi-empirical formula of the ionization frequency is adopted for this model. A transformation of these two equations to local time frame of reference is introduced so that they can be solved numerically with considerably reduced computation time. This model is tested by using it to perform the computer simulation of the experiment. The numerical results are shown to agree well with the experimental results.
Kuo, S. P.↗
Magnetospheric-ionospheric Poynting flux
Over the past three years of funding SRI, in collaboration with the University of Texas at Dallas, has been involved in determining the total electromagnetic energy flux into the upper atmosphere from DE-B electric and magnetic field measurements and modeling the electromagnetic energy flux at high latitudes, taking into account the coupled magnetosphere-ionosphere system. This effort has been very successful in establishing the DC Poynting flux as a fundamental quantity in describing the coupling of electromagnetic energy between the magnetosphere and ionosphere. The DE-B satellite electric and magnetic field measurements were carefully scrutinized to provide, for the first time, a large data set of DC, field-aligned, Poynting flux measurement. Investigations describing the field-aligned Poynting flux observations from DE-B orbits under specific geomagnetic conditions and from many orbits were conducted to provide a statistical average of the Poynting flux distribution over the polar cap. The theoretical modeling effort has provided insight into the observations by formulating the connection between Poynting's theorem and the electromagnetic energy conversion processes that occur in the ionosphere. Modeling and evaluation of these processes has helped interpret the satellite observations of the DC Poynting flux and improved our understanding of the coupling between the ionosphere and magnetosphere.
Thayer, Jeffrey P.↗
Electromagnetic energy transport by tearing fluctuations in a self-organized reversed-field pinch plasma
Fluctuation measurements reveal the outward electromagnetic energy flux needed to drive the dynamo electromotive force supporting magnetic self-organization in a reversed-field pinch plasma. The radial Poynting flux due to tearing mode fluctuations is measured with an insertable probe during magnetic relaxation. This flux corresponds to transient power levels much larger than the input power and comparable to the global equilibrium magnetic energy transient loss rate. The probe measurements of this flux are roughly as predicted by a simple Poynting's theorem model upon substitution of equilibrium measurement data.
Physics↗
The poynting vector in magnetohydrodynamics.
Poynting vector for electromagnetic energy arising from MHD disturbances, specifically for solar wind
SOLAR WIND↗
Energy coupling at a two-fluid plasma density discontinuity.
Energy coupling among electron acoustic, ion acoustic and transverse electromagnetic waves at two-fluid plasma density discontinuity
COUPLED MODE↗