Ulysses Observations of Nonlinear Wave-wave Interactions in the Source Regions of Type III Solar Radio Bursts

AbstractThe Ulysses Unified Radio and Plasma Wave Experiment (URAP) has observed Langmuir, ion-acoustic and associated solar type III radio emissions in the interplanetary medium. Bursts of 50–300 Hz (in the spacecraft frame) electric field signals, corresponding to long-wavelength ion-acoustic waves are often observed coincident in time with the most intense Langmuir wave spikes, providing evidence for the electrostatic decay instability. Langmuir waves often occur as envelope solitons, suggesting that strong turbulence processes, such as modulational instability and soliton formation, often coexist with weak turbulence processes, such as electrostatic decay, in a few type III burst source regions.

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

Nonlinear Processes in Geophysics ◽

10.5194/npg-11-411-2004 ◽

2004 ◽

Vol 11 (3) ◽

pp. 411-420 ◽

Cited By ~ 12

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.

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Detection of Langmuir Solitons: Implications for Type III Burst Emission Mechanisms at 2ωPE

International Astronomical Union Colloquium ◽

10.1017/s0252921100030177 ◽

1996 ◽

Vol 154 ◽

pp. 195-198

Author(s):

G. Thejappa ◽

R.G. Stone ◽

M.L. Goldstein

Keyword(s):

Second Harmonic ◽

Theoretical Models ◽

Burst Source ◽

Langmuir Waves ◽

Type Iii ◽

Source Regions ◽

Envelope Solitons ◽

Turbulence Regime ◽

Solar Type ◽

Langmuir Solitons

AbstractWe present the experimental verification of existing theoretical models of emission mechanisms of solar type III bursts at the second harmonic of the plasma frequency, ωpe. This study is based on the detection of Langmuir and envelope solitons by the Ulysses spacecraft inside three type III burst source regions. We show that the oscillating-two-stream instability, coherent radiation by Langmuir solitons and stochastic phase mixing of the Langmuir waves in the strong turbulence regime are the appropriate emission mechanisms at 2ωpe.

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Modulational stability of ion-acoustic waves using Karpman's method

Canadian Journal of Physics ◽

10.1139/p85-068 ◽

1985 ◽

Vol 63 (4) ◽

pp. 435-436

Author(s):

Bhimsen K. Shivamoggi

Keyword(s):

Acoustic Waves ◽

Modulational Instability ◽

Ion Acoustic Waves ◽

Langmuir Waves ◽

Plasma Motion ◽

Ion Acoustic ◽

Modulational Stability

Karpman's method is explored for the modulational instability of ion-acoustic waves on interaction with a slow plasma motion. The latter are found to be modulationally stable, unlike the Langmuir waves.

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Electron Beams and Langmuir Turbulence in Solar Type III Radio Bursts Observed in the Interplanetary Medium

Symposium - International Astronomical Union ◽

10.1017/s0074180900088471 ◽

1990 ◽

Vol 142 ◽

pp. 467-481

Author(s):

R. P. Lin

Keyword(s):

Interplanetary Medium ◽

Electron Beams ◽

Low Frequency ◽

Langmuir Wave ◽

Plasma Waves ◽

Wave Number ◽

Langmuir Waves ◽

Decay Instability ◽

Type Iii ◽

Solar Type

The ISEE-3 spacecraft has provided in situ observations of electron beams, plasma waves, and associated solar type III radio emission in the interplanetary medium near 1 AU. These observations show that electron beams are formed by the faster electrons arriving before the slower ones, following an impulsive injection at the Sun. The resulting bump-on-tail in the reduced one-dimensional distribution function, f(v||), is unstable to the growth of electrostatic electron plasma (Langmuir) waves. The Langmuir waves are observed to be highly impulsive in nature. The onset and temporal variations of the observed plasma waves are in good qualitative agreement with the wave growth expected from the evolution of measured f(v||). However, far higher Langmuir wave intensities are predicted than are detected. In addition, the lack of obvious plateauing of the bump-on-tail suggests that the waves have been removed from resonance with the beam electrons by some wave-wave interaction. Bursts of low frequency, 30–300 Hz (in the spacecraft frame) waves are often found coincident in time with the most intense spikes of the Langmuir waves. These low-frequency waves appear to be long-wavelength ion acoustic waves, with wave number approximately equal to the beam-resonant Langmuir wave number. The observations suggest several possible interpretations: modulational instability, electrostatic decay instability, and electromagnetic decay instability; but none of these are fully consistent with the observations. Microstructures, too short in duration to be resolved by present experiments, have been invoked as an explanation of the phenomenon. Experiments are currently being developed to study these processes using fast wave-particle correlation techniques.

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Solar Type I Radio Bursts: An Ion-Acoustic Wave Model

Symposium - International Astronomical Union ◽

10.1017/s0074180900036913 ◽

1980 ◽

Vol 86 ◽

pp. 251-254

Author(s):

A. O. Benz ◽

D. G. Wentzel

Keyword(s):

Acoustic Waves ◽

Wave Model ◽

Type I ◽

Radio Bursts ◽

Ion Acoustic Waves ◽

Langmuir Waves ◽

Ion Acoustic Wave ◽

Ion Acoustic ◽

Solar Type ◽

Astronomy And Astrophysics

(paper submitted to Astronomy and Astrophysics)We propose a model for type I emission based on scattering of Langmuir waves by ion acoustic waves, which are associated with the evolution of the associated active region on the Sun.

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