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Excitation of nonlinear upper hybrid waves by O-mode HF heater in the ionospheric heating experiments was explored via HAARP digisonde operated in a fast mode. The observations are manifested by a bump in the virtual spread, which expands the ionogram echoes upward as much as 140 km and is located below the upper hybrid resonance frequency. The bump is similar to that, occurring in daytime ionograms, caused by the cusp at the E-F2 layer transition, indicating that there is a small ledge in the density profile similar to E-F2 layer transitions. The ionograms also show that the virtual height spread, which exceeds 50 km over a significant frequency range below the upper hybrid resonance frequency, is downward, rather than upward as observed in a natural Spread-F situation. It indicates that density irregularities along the geomagnetic field, rather than field-aligned, were generated. Theory shows that the upper hybrid waves excited by the parametric instabilities evolve into nonlinear periodic and solitary waves that enhance downward virtual height spread and generate density cavity to explain the experimental observations. [ABSTRACT FROM AUTHOR]

The acceleration of rotating plasma flow in crossed magnetic fields produced momentum transfer between the macroscopic degrees of freedom for a plasma flow was investigated. Results implied a concept for acceleration of plasma flow containing the charged macroscopic particles. Here, the case is treated when the plasma flow consists of electrons, protons, and heavy, multiply charged negative dust particles only. The analysis shows that these charged macroscopic particles have been trapped and, then, accelerated in the main plasma flow. As a result, such complex plasma flow can be accelerated in one axial direction to increase the thrust. It suggests that such complex plasma flow produced, for example, from cosmic dust medium may be used as a propellant and a work body for plasma thrusters. [ABSTRACT FROM AUTHOR]

Plasma-based microwave power limitation is experimentally investigated in a microstrip transmission line integrating a direct current (dc) plasma discharge for preionization. Steady state and transient high-power microwave measurements demonstrate that the preionization by the dc plasma discharge helps in reducing limiting power thresholds and time responses to about 30 dBm and tens to few microsecond, respectively. Besides, optical diagnostics also exhibit interesting behaviors of the plasma discharge such as diffusion and parasitic breakdowns. Finally, the effect of plasma confinement is discussed, and it is shown that reducing the volume devoted to plasma expansion leads to a decrease in the dynamic range of the microwave power limitation. [ABSTRACT FROM AUTHOR]

Charged particle acceleration is a fundamental issue in many fields ranging from particle physics to spacecraft propulsion. In this paper, the interaction between electromagnetic waves and relativistic electrons is numerically studied. The effect of the initial gyrophase in a dipole magnetic field on electron acceleration by wave--particle interaction is found in a test particle code with various wave amplitudes. It is indicated that the initial gyrophase of the electrons plays a crucial role in the acceleration process. [ABSTRACT FROM AUTHOR]

In the previous investigations, an intermode exchange was used to demonstrate the transfer of energy and momentum into using different kinematic degrees of freedom. This paper examines using a hydrodynamic approach using a cold, neutral flow in a rotating cylindrical plasma column using crossed magnetic fields. Results show that the twirling plasma flow in a cylindrical vortex can be accelerated in an axial direction, thereby resulting an energy/momentum transfer in the axial direction. These results are analogous to the creation of a plasma thruster using this effect. [ABSTRACT FROM PUBLISHER]

The theoretical and numerical studies have been made to observe the planar and nonplanar geometries for the nonlinear propagation of the dust-electron-acoustic (DEA) in a dusty plasma (containing initially cold and hot Maxwellian electrons, stationary ions, and charge fluctuating stationary dust grains) using reductive perturbation method. It has also been found that the basic features of the DEA waves are significantly modified by the presence of dust charge fluctuation. The numerical solution to the K-dV equation indicates that the parameters those we have considered in our model blatantly influence the propagation speed and the structure of DEA solitary waves. The geometrical effects on the structure of DEA wave are discussed. It is shown that the amplitude and propagation speed in spherical geometry is larger compared with cylindrical and planar geometries for different values of the above-mentioned parameters. The implications of our results would be useful to understand some astrophysical and cosmological scenarios like stellar polytropes, hadronic matter and quark-gluon plasma, protoneutron stars, and dark-matter halos. [ABSTRACT FROM PUBLISHER]

In the O-mode high-frequency (HF) heating of the ionosphere, parametric instabilities were excited to generate plasma waves. Among those, Langmuir waves and ion acoustic waves were evidenced by the HF enhanced plasma lines and HF enhanced ion lines in the recorded spectra of the ultra high frequency (UHF)/very high frequency (VHF) backscatter radars. These waves can grow to large amplitudes and become nonlinear waves. The nonlinear Schrodinger equation and Korteweg–de Vries equation governing the nonlinear evolution of Langmuir waves and ion acoustic waves are derived and solved. It is shown that the solutions of these equations can be either periodic or solitary depending on the physical conditions. The analyses show the conditions of generating Langmuir soliton and ion acoustic soliton. [ABSTRACT FROM PUBLISHER]

Nonlinear transmission lines have numerous applications in the communications and defense industries due to their ability to form and propagate short-duration ultrawideband pulses. This paper simulates a short-duration Gaussian transient exciting low-order TEm, 0 modes in a nonlinear ferroelectric-filled conducting waveguide. A 3-D finite-difference time-domain simulation is employed in the analysis, and the ferroelectric-filled waveguide model is based on a nonlinear polarization relationship extrapolated from measurements. A small portion of the frequency band operates in the nonlinear polarization region. These components will propagate at higher velocity than lower amplitude components, and this effect counteracts dispersion and results in compression of the pulses into solitons as they propagate. [ABSTRACT FROM PUBLISHER]

Whistler mode propagation has been studied in a laboratory plasma with nonuniform magnetic fields. The field configurations include magnetic null points and magnetic islands with gradient scale lengths comparable to the wavelength. Oblique whistlers can be trapped on closed field lines when propagating as Gendrin eigenmodes. Whistlers propagate around magnetic nulls. [ABSTRACT FROM AUTHOR]

A highly nonlinear whistler wave packet has been generated in a large laboratory plasma. The wave field exceeds the ambient field, locally reverses its direction and exhibits a topology of a spheromak. It propagates along the ambient magnetic field at a speed that decreases with amplitude. Electrons are strongly energized in the spheromak. Anisotropies create whistler instabilities. The whistler spheromak becomes a propagating source for secondary whistlers, a new phenomenon in magnetic turbulence. [ABSTRACT FROM AUTHOR]