Effect of ambient density fluctuations on Langmuir wave collapse and strong turbulence

1999 ◽  
Vol 6 (8) ◽  
pp. 3057-3065 ◽  
Author(s):  
P. A. Robinson ◽  
G. I. de Oliveira
Keyword(s):  
Langmuir Wave ◽  
Density Fluctuations ◽  
Strong Turbulence ◽  
Wave Collapse

Solar type III radio burst fine structure from Langmuir wave motion through turbulent plasma

2021 ◽  
Author(s):  
Eduard Kontar ◽  
Hamish Reid
Keyword(s):  
Fine Structure ◽  
Solar Corona ◽  
Interplanetary Space ◽  
Langmuir Wave ◽  
Turbulent Medium ◽  
Density Fluctuations ◽  
Solar Radio Emission ◽  
Langmuir Waves ◽  
Type Iii ◽  
Diagnostic Potential

<div>The Sun frequently accelerates near-relativistic electron beams that travel out through the solar corona and interplanetary space. Interacting with their plasma environment, these beams produce type III radio bursts, the brightest astrophysical radio sources detected by humans. The formation and motion of type III fine frequency structures is a puzzle but is commonly believed to be related to plasma turbulence in the solar corona and solar wind. Combining a theoretical framework with kinetic simulations and high-resolution radio type III observations, we quantitatively show that the fine structures are caused by the moving intense clumps of Langmuir waves in a turbulent medium. Our results show how type III fine structure can be used to remotely analyse the intensity and spectrum of compressive density fluctuations, and can infer ambient temperatures in astrophysical plasma, both significantly expanding the current diagnostic potential of solar radio emission.</div><div> </div>

Impossibility of Zakharov's short-wavelength modulational instability in plasmas with intense Langmuir turbulence

2002 ◽  
Vol 68 (1) ◽  
pp. 1-25 ◽  
Author(s):  
V. I. EROFEEV
Keyword(s):  
Experimental Data ◽  
Short Wavelength ◽  
Modulational Instability ◽  
Langmuir Wave ◽  
Traditional Theory ◽  
Langmuir Turbulence ◽  
Wave Dissipation ◽  
Physical Reason ◽  
Electron Diffusion ◽  
Wave Collapse

An analysis of two experimental observations of Langmuir wave collapse is performed. The corresponding experimental data are shown as evidence against the occurrence of collapses. The physical reason preventing the collapses is found to be the nonresonant electron diffusion in momentum. In this process, plasma thermal electrons are efficiently heated at the expense of wave energy, therefore intense collisionless wave dissipation takes place. The basic reason for the underestimation of nonresonant electron diffusion in the traditional theory is shown to be the substitution of a real plasma by a plasma probabilistic ensemble.A study of nonresonant electron diffusion refraining from ensemble substitution is performed. It is shown that its intensity is sufficient for suppression of Zakharov's short-wavelength modulational plasma instability [Zakharov, V. E., Sov. Phys. JETP35, 908 (1972)]. This explains the nonoccurrence of Zakharov's Langmuir wave collapse in experiments.

Experimental investigations of second‐harmonic spectra and Langmuir wave collapse

1991 ◽  
Vol 3 (9) ◽  
pp. 2558-2567 ◽  
Author(s):  
Faiz Dahmani ◽  
Djamel Ghobrini ◽  
Malek EL‐Mahdaoui
Keyword(s):  
Second Harmonic ◽  
Langmuir Wave ◽  
Experimental Investigations ◽  
Wave Collapse

scholarly journals Fundamental Electromagnetic Emissions by a Weak Electron Beam in Solar Wind Plasmas with Density Fluctuations

2022 ◽  
Vol 924 (2) ◽  
pp. L24
Author(s):  
C. Krafft ◽  
P. Savoini
Keyword(s):  
Electron Beam ◽  
Electromagnetic Radiation ◽  
Inhomogeneous Plasma ◽  
Langmuir Wave ◽  
Density Fluctuations ◽  
Electromagnetic Energy ◽  
Langmuir Waves ◽  
Harmonic Emission ◽  
Electromagnetic Emissions ◽  
Weak Electron

Abstract The generation of Langmuir wave turbulence by a weak electron beam in a randomly inhomogeneous plasma and its subsequent electromagnetic radiation are studied owing to two-dimensional particle-in-cell simulations in conditions relevant to type III solar radio bursts. The essential impact of random density fluctuations of average levels of a few percents of the background plasma on the characteristics of the electromagnetic radiation at the fundamental plasma frequency ω p is shown. Not only wave nonlinear interactions but also processes of Langmuir waves’ transformations on the density fluctuations contribute to the generation of such emissions. During the beam relaxation, the amount of electromagnetic energy radiated at ω p in a plasma with density fluctuations strongly exceeds that observed when the plasma is homogeneous. The fraction of Langmuir wave energy involved in the generation of electromagnetic emissions at ω p saturates around 10−4, i.e., one order of magnitude above that reached when the plasma is uniform. Moreover, whereas harmonic emission at 2ω p dominates over fundamental emission during the time evolution in a homogeneous plasma, fundamental emission is strongly dominant when the plasma contains density fluctuations, at least during several thousands of plasma periods before being overcome by harmonic emission when the total electromagnetic energy begins to saturate.

Dynamics of Langmuir Wave Spectra in Randomly Inhomogeneous Solar Wind Plasmas

2021 ◽  
Vol 923 (1) ◽  
pp. 103
Author(s):  
C. Krafft ◽  
A. S. Volokitin
Keyword(s):  
Diffusion Processes ◽  
Langmuir Wave ◽  
Density Fluctuations ◽  
Wave Turbulence ◽  
Quasi Particle ◽  
Potential Fluctuations ◽  
The Earth ◽  
Self Consistent ◽  
Electromagnetic Emissions ◽  
Non Gaussian

Abstract Solar coronal and wind plasmas often contain density fluctuations of various scales and amplitudes. The scattering of Langmuir wave turbulence on these inhomogeneities modifies the properties of the radiated electromagnetic emissions traveling from the Sun to the Earth. This paper shows the similarities between the physical results obtained by (i) a model based on the Zakharov equations, describing the self-consistent dynamics of Langmuir wave turbulence spectra in a plasma with external density fluctuations, and (ii) a modeling, within the framework of geometric optics approximation, of quasi-particles (representing plasmon quanta) moving in a fluctuating potential. It is shown that the dynamics of the Langmuir spectra is governed by anomalous diffusion processes, as a result of multiple scattering of waves on the density fluctuations; the same dynamics are observed in the momenta distributions of quasi-particles moving in potential structures with random inhomogeneities. These spectra and distributions are both characterized by a fast broadening during which energy is transported to larger wavevectors and momenta, exhibiting nonlinear time dependence of the average squares of wavevectors and quasi-particle momenta as well as non-Gaussian tails in the asymptotic stage. The corresponding diffusion coefficients depend on the time and are proportional to the square of the average level of density (or potential) fluctuations. It appears that anomalous transport and superdiffusion phenomena are responsible for the spectral broadening.

Evidence for Langmuir wave collapse in the interplanetary plasma

1992 ◽  
Vol 19 (12) ◽  
pp. 1303-1306 ◽  
Author(s):  
Paul J. Kellogg ◽  
K. Goetz ◽  
R. L. Howard ◽  
S. J. Monson
Keyword(s):  
Langmuir Wave ◽  
Wave Collapse ◽  
Interplanetary Plasma
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