On natural noises detected by antennas in plasmas

Meyer‐Vernet, N.

doi:10.1029/ja084ia09p05373

Cited by 138 publications

(66 citation statements)

References 16 publications

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“…(1) and (2), or equivalently, by balancing spontaneous and induced emissions. [16][17][18][19] The resulting thermal intensities can, of course, be computed on the basis of the fluctuation-dissipation theorem. The initial spectra thus computed are given by…”

Section: Numerical Analysismentioning

confidence: 99%

Transition from thermal to turbulent equilibrium with a resulting electromagnetic spectrum

et al. 2014

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A recent paper [Ziebell et al., Phys. Plasmas 21, 010701 (2014)] discusses a new type of radiation emission process for plasmas in a state of quasi-equilibrium between the particles and enhanced Langmuir turbulence. Such a system may be an example of the so-called “turbulent quasi-equilibrium.” In the present paper, it is shown on the basis of electromagnetic weak turbulence theory that an initial thermal equilibrium state (i.e., only electrostatic fluctuations and Maxwellian particle distributions) transitions toward the turbulent quasi-equilibrium state with enhanced electromagnetic radiation spectrum, thus demonstrating that the turbulent quasi-equilibrium discussed in the above paper correctly describes the weakly turbulent plasma dynamically interacting with electromagnetic fluctuations, while maintaining a dynamical steady-state in the average sense.

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Section: Numerical Analysismentioning

confidence: 99%

Transition from thermal to turbulent equilibrium with a resulting electromagnetic spectrum

et al. 2014

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“…This last is a measure of the fluctuations of electron density. The Whisper experiment measures the spectrum of Langmuir oscillations in equilibrium with the quasi-thermal plasma, (Meyer-Vernet, 1979;Kellogg, 1981;Meyer-Vernet and Perche, 1989) which provides a measure of plasma density which is relatively independent of spacecraft perturbations of the plasma, since the Langmuir waves at the lowest frequencies have wavelengths very long compared to the size of the disturbed region. When the spacecraft are in the foreshock region, i.e.…”

Section: Observationsmentioning

confidence: 99%

Rapid density fluctuations in the solar wind

Kellogg

Horbury

2005

Ann. Geophys.

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Abstract. Electron density fluctuations (up to 2.5 Hz) in the solar wind have been studied, using the EFW experiment on the Cluster spacecraft, which measures density through measurements of the biased probe potentials relative to the spacecraft. The density fluctuation spectra obtained from the EFW probe potential variations are compared to earlier, OGO 5, measurements of ion density fluctuations and ISEE measurements of electron density fluctuations, and are consistent with them. The electric fields corresponding to the electron density fluctuations are extremely small compared with what would be obtained if the electron fluctuations were not cancelled out by nearly equal ion density fluctuations. This is consistent with the nature of ion acoustic waves. In agreement with ISEE work, the fluctuations are proportional to the ambient density. Correlation with magnetic fluctuations is weak, essentially nonexistent during part of the period studied. This might be expected as magnetic fluctuations are known to be nearly incompressible, but even the correlation with fluctuations in the magnitude of B is very small. However, many structures which apparently are pressure balance structures are found. Pressure balance structures are the nearly perpendicular propagation limit of ion acoustic waves.As ion acoustic waves are strongly damped in plasmas like the solar wind at least if the plasma is taken as Maxwellian, it has always been a puzzle as to why they are found there. We speculate that these waves are created by mode conversion from magnetic fluctuations, and may represent part of the dissipation process for these.

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“…It also involves nonlinear extension of the customary theory of thermal fluctuations. 5,6 According to the standard theory, unmagnetized thermal plasmas emit electrostatic fluctuation according to the formula (which is, in fact, the Cerenkov emission formula)…”

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confidence: 99%

“…One of them is the so-called quasi-thermal noise (QTN). 6 It is well known that the solar-terrestrial environment is replete with various radio signals and noises. QTN is often interpreted as electrostatic Langmuir-type fluctuations, which is reasonable given the antenna geometry and dimensional limitations, but there is a likelihood that EM component may exist in such fluctuations [N. MeyerVernet, private communication].…”

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confidence: 99%