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Magnetoplasma characteristics - anomalous diffusion across magnetic field, heat conduction in plasma, cesium plasma generator, and electron velocity distribution function in magnetoplasmas
The effects of thermal motions on the cyclotron radiation from test particles gyrating in a homogeneous magnetoplasma are studied. These effects take care of all singularities that exist in the theory of cyclotron radiation in cold magnetoplasma - e.g., the divergence in energy loss for small particle energies. Around the hybrid frequencies thermal corrections become of dominant importance. At these frequencies cold-plasma theory breaks down. Thermal effects arise in two ways: by modifying the wave modes known from cold plasma theory, and by the introduction of a new longitudinal wave mode, known as the Bernstein mode. All wave modes are damped (in stable plasmas).
Linear and nonlinear responses of a magnetoplasma resulting from inhomogeneity in the background plasma density are studied. The plasma response to an impulse electric field was measured and the results are compared with the theory of an inhomogeneous cold plasma. Impulse responses were recorded for the different plasma densities, static magnetic fields, and neutral pressures and generally appeared as modulated, damped oscillations. The frequency spectra of the waveforms consisted of two separated resonance peaks. For weak excitation, the results correlate with the linear theory of a cold, inhomogeneous, cylindrical magnetoplasma. The damping mechanism is identified with that of phase mixing due to inhomogeneity in plasma density. With increasing excitation voltage, the nonlinear impulse responses display stronger damping and a small increase in the frequency of oscillation.
The basis of the theory of waves in a cold homogeneous magnetoplasma is reviewed. The radio approximation (associated with Appleton) applies when the wave-frequency is large compared with the geometric mean of the electronic and ionic gyrofrequencies. The hydromagnetic approximation (associated with Alfven) corresponds to infinite conductivity along the lines of flux of the imposed magnetic field and applies when the wave-frequency is small compared with the plasma-frequency. The rich variety of dispersion phenomena existing in a magnetoplasma is illustrated by polar diagrams showing both the variation of group-velocity with beam-direction and the direction in which the antenna must be pointed to aim a beam in a particular direction.
A theory has been developed for the impedance of a homogeneous magnetoplasma enclosed between two specular reflecting coaxial electrodes, with a static magnetic field parallel to the electrode axes. The parallel-plate magnetoplasma capacitor is treated as a sub-case. Starting with the Vlasov equation, an integral equation is derived for the electric field. Solving this equation, and integrating to obtain the voltage, gives the capacitor impedance. This includes a capacitive component, and a resistive component expressing the Landau damping associated with the open orbits of electrons reflected at the electrodes. A direct numerical solution of the field integral equation has been carried out for a range of values of magnetic field, plasma density, and signal frequency. The values of impedance so obtained are compared with the predictions of macroscopic theory, and of an approximate microscopic theory in which open orbits are ignored and solutions are obtained using finite Fourier transform methods. The mathematical relations between these theories are demonstrated.
The effect of a time-dependent perturbation in the magnetoplasma on the wave and particle populations is investigated using the Kennel-Petchek (1966) approach. Perturbations in the cold plasma density, energetic particle distribution, and resonance condition are calculated on the basis of the ideal MHD assumption given an arbitrary compressional magnetic field perturbation. An equation is derived describing the time-dependent growth rate for parallel propagating electromagnetic cyclotron waves in a time-varying magnetoplasma with perturbations superimposed on an equilibrium configuration.
Dynamics of plasma current sheath and magnetosonic resonance in magnetoplasmas
Metal X-band waveguide cell for study of microwave propagation through magnetoplasma
Radiation properties in homogeneous magnetoplasma as result of dispersive anisotropic nature of medium
Electric breakdown and current sheath formation and acceleration in magnetoplasmas
Antenna radiation field in magnetoplasma in terms of normalized characteristic plane waves
Metal X-band circular waveguide cell containing discharge electrodes for study of microwave propagation in magnetoplasma
Radiation patterns of infinitesimal dipole in lossless magnetoplasma studied by classification of associated dispersion surfaces
Magnetoplasma electron emission in whistler mode frequency band and extraordinary mode frequency band around plasma frequency where refractive indices are greater than one
Separation method solution of dyadic-vector Helmholtz equation representing electromagnetic wave propagation in bounded magnetoplasmas
Cavity resonance measurement of Faraday rotation of microwaves in gaseous magnetoplasma
Magnetoplasma diffusion equation derivation for F-2 layer of ionosphere
Combination scattering of electromagnetic waves from driven space charge waves in magnetoplasma