Harmonic Langmuir waves. II. Turbulence spectrum

Electromagnetic radiation at the plasma frequency and/or its second harmonic, the so-called plasma emission, is widely accepted as the fundamental process responsible for solar type II and III radio bursts. There have also been occasional observations of higher-harmonic plasma emissions in the solar-terrestrial environment. This paper presents the first demonstration of multiple harmonic emission by means of twodimensional electromagnetic particle-in-cell simulation. This finding indicates that under certain circumstances the traditional mechanism of fundamental-harmonic pair emission might also be accompanied by higher-harmonic components. Consequently, the present findings are highly relevant to in situ observations of third-and/or higher-harmonic plasma emission in astrophysical and solar-terrestrial environments.

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“…Their theory (which is essentially similar to that proposed by Gaelzer et al 2003) does, however, explain why 2L, 3L, . .…”

Section: Discussionmentioning

confidence: 63%

Multiple harmonic plasma emission

Yoon

Ryu

2007

Physics of Plasmas

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“…Since the waves are enhanced to a nonthermal level, we expect second harmonics to be noticeable, as indeed observed. 29,45,46 …”

Section: -5mentioning

confidence: 99%

Nonlinear beam generated plasma waves as a source for enhanced plasma and ion acoustic lines

et al. 2011

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Observations by, for instance, the EISCAT Svalbard Radar (ESR) demonstrate that the symmetry of the naturally occurring ion line in the polar ionosphere can be broken by an enhanced, nonthermal, level of fluctuations (naturally enhanced ion-acoustic lines, NEIALs). It was in many cases found that the entire ion spectrum can be distorted, also with the appearance of a third line, corresponding to a propagation velocity significantly slower than the ion acoustic sound speed. It has been argued that selective decay of beam excited primary Langmuir waves can explain some phenomena similar to those observed. We consider a related model, suggesting that a primary nonlinear process can be an oscillating two-stream instability, generating a forced low frequency mode that does not obey any ion sound dispersion relation. At later times, the decay of Langmuir waves can give rise also to enhanced asymmetric ion lines. The analysis is based on numerical results, where the initial Langmuir waves are excited by a cold dilute electron beam. By this numerical approach, we can detect fine details of the physical processes, in particular, demonstrate a strong space-time intermittency of the electron waves in agreement with observations. Our code solves the full Vlasov equation for electrons and ions, with the dynamics coupled through the electrostatic field derived from Poisson's equation. The analysis distinguishes the dynamics of the background and beam electrons. This distinction simplifies the analysis for the formulation of the weakly nonlinear analytical model for the oscillating two-stream instability. The results have general applications beyond their relevance for the ionospheric observations.

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“…Recently, however, a theory of harmonic generation in turbulent plasmas was developed by the author and his colleagues (Yoon, 2000;Gaelzer et al, 2002Gaelzer et al, , 2003Yoon et al, 2003;Umeda et al, 2003), in which these modes are considered as eigenmodes of nonlinear plasma system. This approach was prompted by recent simulations (Schriver et al, 2000;Kasaba et al, 2001) which show that harmonic modes persist even in late nonlinear phase when the coherent phase space structure is no longer apparent, and when the plasma has entered a stage which can be genuinely characterized by random-phases.…”

Section: Harmonic Langmuir Modesmentioning

confidence: 99%

Formation of quasi-power law weak Langmuir turbulence spectrum by harmonic generation

Yoon

2004

Nonlin. Processes Geophys.

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Abstract. Langmuir wave turbulence generated by a beamplasma interaction has been studied since the early days of plasma physics research. Despite a long history of investigation on this subject, among the outstanding issues is the generation of harmonic Langmuir waves observed in both laboratory and computer-simulated experiments. However, the phenomenon has not been adequately explained in terms of theory, nor has it been fully characterized by means of numerical simulations. In this paper, a theory of harmonic Langmuir wave generation is put forth and tested against the Vlasov simulation results. It is found that the harmonic Langmuir mode spectra exhibit quasi power-law feature implying a multi-scale structure in both frequency and wave number space spanning several orders of magnitude.

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Harmonic Langmuir waves. II. Turbulence spectrum

Cited by 50 publications

References 35 publications

Multiple harmonic plasma emission

Multiple harmonic plasma emission

Nonlinear beam generated plasma waves as a source for enhanced plasma and ion acoustic lines

Formation of quasi-power law weak Langmuir turbulence spectrum by harmonic generation

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