skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Laboratory Study of Nonlinear Trapping of Magnetized Langmuir Waves Inside a Density Depletion

Abstract

The formation of a small-scale plasma density depletion region extended along the ambient magnetic field and caused by the nonlinear interaction of the upper-hybrid plasma waves with a magnetoplasma has been observed under laboratory conditions modeling the ionospheric heating experiments. Plasma waves are trapped inside the depletion due to their specific dispersion properties. The threshold of the nonlinear wave trapping significantly increases in the vicinity of the harmonics of the electron gyrofrequency.

Authors:
; ;  [1]
  1. Institute of Applied Physics, Russian Academy of Science, 46 Ulyanov Street, 603950 Nizhny Novgorod (Russian Federation)
Publication Date:
OSTI Identifier:
20951354
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 19; Other Information: DOI: 10.1103/PhysRevLett.98.195001; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ELECTRONS; GYROFREQUENCY; HARMONICS; LANGMUIR FREQUENCY; MAGNETIC FIELDS; NONLINEAR PROBLEMS; PLASMA; PLASMA DENSITY; PLASMA SIMULATION; PLASMA WAVES; TRAPPING

Citation Formats

Starodubtsev, Mikhail V., Nazarov, Vladimir V., and Kostrov, Alexander V. Laboratory Study of Nonlinear Trapping of Magnetized Langmuir Waves Inside a Density Depletion. United States: N. p., 2007. Web. doi:10.1103/PHYSREVLETT.98.195001.
Starodubtsev, Mikhail V., Nazarov, Vladimir V., & Kostrov, Alexander V. Laboratory Study of Nonlinear Trapping of Magnetized Langmuir Waves Inside a Density Depletion. United States. doi:10.1103/PHYSREVLETT.98.195001.
Starodubtsev, Mikhail V., Nazarov, Vladimir V., and Kostrov, Alexander V. Fri . "Laboratory Study of Nonlinear Trapping of Magnetized Langmuir Waves Inside a Density Depletion". United States. doi:10.1103/PHYSREVLETT.98.195001.
@article{osti_20951354,
title = {Laboratory Study of Nonlinear Trapping of Magnetized Langmuir Waves Inside a Density Depletion},
author = {Starodubtsev, Mikhail V. and Nazarov, Vladimir V. and Kostrov, Alexander V.},
abstractNote = {The formation of a small-scale plasma density depletion region extended along the ambient magnetic field and caused by the nonlinear interaction of the upper-hybrid plasma waves with a magnetoplasma has been observed under laboratory conditions modeling the ionospheric heating experiments. Plasma waves are trapped inside the depletion due to their specific dispersion properties. The threshold of the nonlinear wave trapping significantly increases in the vicinity of the harmonics of the electron gyrofrequency.},
doi = {10.1103/PHYSREVLETT.98.195001},
journal = {Physical Review Letters},
number = 19,
volume = 98,
place = {United States},
year = {Fri May 11 00:00:00 EDT 2007},
month = {Fri May 11 00:00:00 EDT 2007}
}
  • Nonlinear interaction of Langmuir waves with a laboratory magnetoplasma has been studied under the conditions relevant to the ionospheric heating experiments. Self-guiding of magnetized Langmuir waves is observed at critical plasma density ({omega}={omega}{sub p}): Langmuir waves are trapped inside a narrow, magnetic-field-aligned plasma density depletion region, which is formed by trapped waves due to thermal plasma nonlinearity, i.e., due to local plasma heating and consequent thermodiffusion. Magnetized Langmuir waves are trapped inside the depletion region through their specific dispersion properties; this fact has been shown using the kinetically modified dispersion relation. The threshold of the nonlinear wave trapping exhibits significantmore » growth in the vicinity of harmonics of the electron gyrofrequency.« less
  • The propagation of slightly nonlinear electron-density waves in a waveguide filled with a magnetized plasma is analyzed. It is assumed that the nonlinearity, the dispersion, and the dissipation are slight. Then the original nonlinear system of Vlasov--Poisson equations is reduced to a system of evolutionary equations of the Korteweg--de Vries type for the amplitudes of the waveguide modes. This system has a nonlocal term describing collisionless damping. In the case in which there is no mode degeneracy it is found that for only certain of these modes does a finite initial perturbation evolve to Korteweg--de Vries solitons. The conditions formore » soliton amplification in the beam--plasma system are discussed.« less
  • The diffusion-limited kinetics of the growth of a depletion zone around a static point trap in a thin, long channel geometry was studied using a laser photobleaching experiment of fluorescein dye inside a flat rectangular capillary. The dynamics of the depletion zone was monitored by the {theta} distance, defined as the distance from the trap to the point where the reactant concentration has been locally depleted to the specified survival fraction ({theta}) of its initial bulk value. A dimensional crossover from two dimensions to one dimension, due to the finite width of the reaction zone, was observed. We define amore » 'parallel' and a 'perpendicular' {theta} distance, along the slab long and short dimensions, respectively, and study their time development as a means to study the asymmetrical nature of the slab geometry. For all {theta} values, the crossover occurs concurrently for both {theta} distances when the depletion zone touches the boundary for the first time. We derive theoretical expressions for this geometry and compare them with the experimental data. We also obtain important insight from the ratio of the reactant concentration profiles in the parallel and perpendicular directions. Exact enumeration and Monte Carlo simulations support the anomalous depletion scaling results. Nevertheless, the crossover time ({tau}{sub c}) is still found to scale with the width (W) of the rectangular reaction zone as {tau}{sub c}{approx}W{sup 2}, as expected from the basic Einstein diffusion law.« less
  • Anti-Stokes Langmuir waves were observed in the ionospheric plasma heating experiments at Arecibo, Puerto Rico. They are referred to as frequency upshifted Langmuir waves excited by injected high power HF waves. The frequency shifts are found to be inversely proportional to the HF pump wave frequencies, and of the magnitudes of the lower hybrid wave frequencies in the ionosphere. Kuo and Lee suggest that these anti-Stokes Langmuir waves are caused by the nonlinear scattering of HF wave-produced Langmuir waves off lightning-induced lower hybrid waves. Laboratory experiments with a large toroidal plasma machine known as the Versatile Toroidal Facility (VTF) havemore » been conducted to investigate this nonlinear scattering process. In VTF, a background plasma is created by a Taylor discharge device which has a peak plasma frequency greater than the electron gyro-frequency by a factor of 3--5. This factor has been chosen in order to simulate the ionospheric plasma environment. Overdense heating of the VTF plasma by injected microwaves can generate Langmuir waves and ion acoustic waves via the decay instability. These Langmuir waves may then be scattered by lower hybrid turbulence existing in the background VTF plasmas to produce the anti-Stokes modes. Preliminary results of the laboratory experiments are presented and compared with results of field experiments and theory.« less
  • A study was made of a parametric instability in a magnetized plasma in which an electromagnetic pump wave of either right- or left-hand circular polarization decayed into a Langmuir wave and another circularly polarized wave, all with wave vectors colinear with the external magnetic field. The analysis was based on a multiple-time- scale perturbation expansion of the fluid equations, incorporating the effects of temperature, collisions, and the spatial variation of the pump wave. The threshold values of the pump field intensity required for instability and the growth rates above threshold were calculated. (auth)