scholarly journals Parametric Decay of Beam‐Generated Langmuir Waves and Three‐Wave Interaction in Plateau Plasmas: Implications for Type III Radiation

2019 ◽  
Vol 124 (1) ◽  
pp. 68-89 ◽  
Author(s):  
Konrad Sauer ◽  
Klaus Baumgärtel ◽  
Richard Sydora ◽  
Daniel Winterhalter
Keyword(s):  
Wave Interaction ◽  
Langmuir Waves ◽  
Type Iii ◽  
Parametric Decay

scholarly journals Polarization and Position Measurements of Type III Bursts

1980 ◽  
Vol 86 ◽  
pp. 315-322 ◽  
Author(s):  
S. Suzuki ◽  
G.A. Dulk ◽  
K. V. Sheridan
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Open Field ◽  
Langmuir Waves ◽  
Type Iii ◽  
Brightness Temperatures ◽  
Polarization Characteristics ◽  
Field Lines ◽  
Cosine Law ◽  
The Magnetic Field

We report on the positional and polarization characteristics of Type III bursts in the range 24–220 MHz as measured by the Culgoora radioheliograph, spectrograph and spectropolarimeter. Our study includes 997 bursts which are of two classes: fundamental-harmonic (F-H) pairs and “structureless” bursts with no visible F-H structure. In a paper published elsewhere (Dulk and Suzuki, 1979) we give a detailed description and include observations of source sizes, heights and brightness temperatures. Here we concentrate on the polarization of the bursts and the variation of polarization from centre to limb. The observed centre-to-limb decrease in polarization approximately follows a cosine law. This decrease is not as predicted by simple theory but is consistent with other observations which imply that open field lines from an active region diverge strongly. The observed o-mode polarization of harmonic radiation implies that the wave vectors of Langmuir waves are always parallel, within about 20°, to the magnetic field, while the constancy of H polarization with frequency implies that the ratio fB/fP, the Alfvén speed vA and the plasma beta are constant with height on the open field lines above an active region. Finally, we infer that some factor, in addition to the magnetic field strength, controls the polarization of F radiation.

scholarly journals High frequency ion sound waves associated with Langmuir waves in type III radio burst source regions

2004 ◽  
Vol 11 (3) ◽  
pp. 411-420 ◽  
Author(s):  
G. Thejappa ◽  
R. J. MacDowall
Keyword(s):  
Short Wavelength ◽  
Langmuir Wave ◽  
Linear Process ◽  
Radio Bursts ◽  
Sound Waves ◽  
Burst Source ◽  
Langmuir Waves ◽  
Type Iii ◽  
Resonant Wave ◽  
Source Regions

Abstract. Short wavelength ion sound waves (2-4kHz) are detected in association with the Langmuir waves (~15-30kHz) in the source regions of several local type III radio bursts. They are most probably not due to any resonant wave-wave interactions such as the electrostatic decay instability because their wavelengths are much shorter than those of Langmuir waves. The Langmuir waves occur as coherent field structures with peak intensities exceeding the Langmuir collapse thresholds. Their scale sizes are of the order of the wavelength of an ion sound wave. These Langmuir wave field characteristics indicate that the observed short wavelength ion sound waves are most probably generated during the thermalization of the burnt-out cavitons left behind by the Langmuir collapse. Moreover, the peak intensities of the observed short wavelength ion sound waves are comparable to the expected intensities of those ion sound waves radiated by the burnt-out cavitons. However, the speeds of the electron beams derived from the frequency drift of type III radio bursts are too slow to satisfy the needed adiabatic ion approximation. Therefore, some non-linear process such as the induced scattering on thermal ions most probably pumps the beam excited Langmuir waves towards the lower wavenumbers, where the adiabatic ion approximation is justified.

Scattering of Langmuir waves produced by a beam with finite transverse dimensions

1972 ◽  
Vol 7 (3) ◽  
pp. 523-543
Author(s):  
G. Berthomieu
Keyword(s):  
Simple Model ◽  
Plasma Waves ◽  
Radio Bursts ◽  
Nonlinear Processes ◽  
Langmuir Waves ◽  
Type Iii

It has been proposed by Smith that type III radio bursts may be produced by streams of protons with radius of the order of 7 km, which is of the same order as the characteristic lengths of the nonlinear processes which are supposed to take place in the dynamics of these bursts. In this paper, we consider a method for studying systems with finite transverse dimensions and apply it to a simple model: the scattering of a beam of plasma waves by acoustic turbulence and by the particles of the plasma.

scholarly journals A Relationship Between the Brightness Temperatures for Type III Bursts

1974 ◽  
Vol 57 ◽  
pp. 285-287
Author(s):  
D. B. Melrose
Keyword(s):  
Fundamental Frequency ◽  
Solar Phys ◽  
Second Harmonic ◽  
Intermediate Stage ◽  
Langmuir Waves ◽  
Type Iii ◽  
Brightness Temperatures ◽  
Two Stages

(Solar Phys.). The widely accepted emission mechanisms for type III bursts involve at least two stages. The first stage is the generation of Langmuir waves by the inferred stream of electrons. Emission at the fundamental frequency arises when these waves are scattered by thermal ions. Emission at the second harmonic arises when two Langmuir waves coalesce; however, the coalescence is possible only after an intermediate stage in which the distribution of Langmuir waves evolves towards isotropy due to scattering by thermal ions.

Generation of Langmuir waves by nonlinear wave-wave interaction in the ionosphere

1981 ◽  
Vol 86 (A6) ◽  
pp. 4731-4738 ◽  
Author(s):  
J. C. Cerisier ◽  
J. Lavergnat ◽  
J. J. Rihouey ◽  
R. Pellat
Keyword(s):  
Nonlinear Wave ◽  
Wave Interaction ◽  
Langmuir Waves
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