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Title: Wave-wave interactions in solar type III radio bursts

Abstract

The high time resolution observations from the STEREO/WAVES experiment show that in type III radio bursts, the Langmuir waves often occur as localized magnetic field aligned coherent wave packets with durations of a few ms and with peak intensities well exceeding the strong turbulence thresholds. Some of these wave packets show spectral signatures of beam-resonant Langmuir waves, down- and up-shifted sidebands, and ion sound waves, with frequencies, wave numbers, and tricoherences satisfying the resonance conditions of the oscillating two stream instability (four wave interaction). The spectra of a few of these wave packets also contain peaks at f{sub pe}, 2f{sub pe} and 3 f{sub pe} (f{sub pe} is the electron plasma frequency), with frequencies, wave numbers and bicoherences (computed using the wavelet based bispectral analysis techniques) satisfying the resonance conditions of three wave interactions: (1) excitation of second harmonic electromagnetic waves as a result of coalescence of two oppositely propagating Langmuir waves, and (2) excitation of third harmonic electromagnetic waves as a result of coalescence of Langmuir waves with second harmonic electromagnetic waves. The implication of these findings is that the strong turbulence processes play major roles in beam stabilization as well as conversion of Langmuir waves into escaping radiationmore » in type III radio bursts.« less

Authors:
 [1];  [2]
  1. Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)
  2. NASA/Goddard Space Flight Center, Greenbelt MD 20771 (United States)
Publication Date:
OSTI Identifier:
22263919
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1582; Journal Issue: 1; Conference: International conference on complex processes in plasmas and nonlinear dynamical systems, Gandhinagar (India), 6-9 Nov 2012; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; COALESCENCE; ELECTROMAGNETIC RADIATION; INTERACTIONS; LANGMUIR FREQUENCY; MAGNETIC FIELDS; PEAKS; RESONANCE; SOUND WAVES; SPECTRA; TIME RESOLUTION; TURBULENCE; TWO-STREAM INSTABILITY; WAVE PACKETS

Citation Formats

Thejappa, G., and MacDowall, R. J. Wave-wave interactions in solar type III radio bursts. United States: N. p., 2014. Web. doi:10.1063/1.4865358.
Thejappa, G., & MacDowall, R. J. Wave-wave interactions in solar type III radio bursts. United States. doi:10.1063/1.4865358.
Thejappa, G., and MacDowall, R. J. 2014. "Wave-wave interactions in solar type III radio bursts". United States. doi:10.1063/1.4865358.
@article{osti_22263919,
title = {Wave-wave interactions in solar type III radio bursts},
author = {Thejappa, G. and MacDowall, R. J.},
abstractNote = {The high time resolution observations from the STEREO/WAVES experiment show that in type III radio bursts, the Langmuir waves often occur as localized magnetic field aligned coherent wave packets with durations of a few ms and with peak intensities well exceeding the strong turbulence thresholds. Some of these wave packets show spectral signatures of beam-resonant Langmuir waves, down- and up-shifted sidebands, and ion sound waves, with frequencies, wave numbers, and tricoherences satisfying the resonance conditions of the oscillating two stream instability (four wave interaction). The spectra of a few of these wave packets also contain peaks at f{sub pe}, 2f{sub pe} and 3 f{sub pe} (f{sub pe} is the electron plasma frequency), with frequencies, wave numbers and bicoherences (computed using the wavelet based bispectral analysis techniques) satisfying the resonance conditions of three wave interactions: (1) excitation of second harmonic electromagnetic waves as a result of coalescence of two oppositely propagating Langmuir waves, and (2) excitation of third harmonic electromagnetic waves as a result of coalescence of Langmuir waves with second harmonic electromagnetic waves. The implication of these findings is that the strong turbulence processes play major roles in beam stabilization as well as conversion of Langmuir waves into escaping radiation in type III radio bursts.},
doi = {10.1063/1.4865358},
journal = {AIP Conference Proceedings},
number = 1,
volume = 1582,
place = {United States},
year = 2014,
month = 2
}
  • The emission of fundamental and harmonic frequency radio waves of type II radio bursts are assumed to be products of three-wave interaction processes of beam-excited Langmuir waves. Using a particle-in-cell code, we have performed simulations of the assumed emission region, a coronal mass ejection foreshock with two counterstreaming electron beams. Analysis of wavemodes within the simulation shows self-consistent excitation of beam-driven modes, which yield interaction products at both fundamental and harmonic emission frequencies. Through variation of the beam strength, we have investigated the dependence of energy transfer into electrostatic and electromagnetic modes, confirming the quadratic dependence of electromagnetic emission onmore » electron beam strength.« less
  • Type I solar radio bursts result from the sudden liberation of vibrational energy which has accumulated in the plasma of the solar corona due to nonlinear ordinary-wave trapping in the potential well formed under the influence of the rf pressure of this wave on the magnetized plasma. A slight instability in the plasma is an adequate energy source. The nature of this potential well is found; it is a three-dimensional ordinary-wave soliton. The maximum energy density for which such a soliton can exist is estimated. A large number of such solitons can accumulate in the corona as a result ofmore » an instability. This mechanism explains the basic features of type I bursts: their pulsed nature, the narrow emission band, the polarization, the direction, etc.« less
  • Induced scattering of plasma waves into electromagnetic waves may be neglected as a factor contributing to high frequency type III radio bursts if their brightness temperature is below 10/sup 10/ /sup 0/K. Spontaneous scattering of plasma waves by thermal coronal ions will produce the fundamental-mode radiation. At frequencies near 200 MHz, over 90 percent of all observed type III bursts satisfy the condition T/sub b/ less than 10/sup 10/ /sup 0/K.
  • Assuming that type III solar radio bursts are associated with electron streams moving at about c/3, Langmuir waves should be strongly excited. We have studied all of the Langmuir-wave linear parametric instabilities excited in cylindrical symmetry by an electron-stream--driven Langmuir wave-pump propagating along the stream axis. Included in this unified homogeneous treatment are induced backscattering off ions, the oscillating two-stream instability, and a new ''stimulated modulational instability,'' previously unconsidered in this context. Near a few solar radii, the latter two deposit Langmuir wave energy into a forward-scattering cone about the stream axis. It is concluded that the linear stage ofmore » the forward-scattering instabilities involves transfer of energy to Langmuir waves which remain in resonance with the stream, and therefore probably do not prevent rapid depletion of the electron stream due to quasilinear plateau formation at these distances from the Sun. (AIP)« less