Nonlinear wave interactions as a model for naturally enhanced ion acoustic lines in the ionosphere

Kontar, Eduard P.; Pécseli, H. L.

doi:10.1029/2004gl022182

Cited by 12 publications

(15 citation statements)

References 20 publications

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“…Those results rely on an entirely different computational model 60 based on the weak turbulence approximation. We have studied more localized density gradients in ion density, but these were of scale lengths too short to be relevant for those previous studies, 17,18 and no conclusive results can be presented. Finally, we emphasize that our results have applications beyond their relevance for the ionospheric observations and apply for electrostatic plasma waves generated by low density cold electron beams in collisionless plasmas.…”

Section: Discussionmentioning

confidence: 99%

“…Other studies 17,18 indicated that these effects could be important. Those results rely on an entirely different computational model 60 based on the weak turbulence approximation.…”

Section: Discussionmentioning

confidence: 99%

“…The effects connected with plasma inhomogeneity have been largely ignored, although a consistent treatment of the ionospheric plasma density gradient can bring new understanding of the observational results. 17,18 The ionospheric observations as such seem to be unambiguous, 3 but the interpretation is made difficult by several practical problems: the observed features are often sporadic in nature, and can vary with time as well as altitude, on second and kilometer scales, respectively. 1,12 We bear in mind that the radar is usually obtaining backscatter at one selected wavevector k R , which is related to the scattering wavevector k B by selection rules, which for a monostatic radar gives k B ¼ 2k R .…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Discussionmentioning

confidence: 99%

“…Other studies 17,18 indicated that these effects could be important. Those results rely on an entirely different computational model 60 based on the weak turbulence approximation.…”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2011

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“…Several theories have emerged in order to explain the source of NEIALs, namely the electron-ion and ion-ion two-stream instabilities as well as nonlinear wave-wave interactions (via Langmuir decay). The enhanced ion-acoustic fluctuations due to parametric decay of Langmuir waves remains the most promising, at least for explaining some observed features (see Kontar and Pécseli, 2005, and references therein).…”

Section: Application and Discussionmentioning

confidence: 99%

Nonlocal nonlinear coupling of kinetic sound waves

Lyubchyk

Voitenko

2014

Ann. Geophys.

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Abstract. We study three-wave resonant interactions among kinetic-scale oblique sound waves in the low-frequency range below the ion cyclotron frequency. The nonlinear eigenmode equation is derived in the framework of a twofluid plasma model. Because of dispersive modifications at small wavelengths perpendicular to the background magnetic field, these waves become a decay-type mode. We found two decay channels, one into co-propagating product waves (forward decay), and another into counter-propagating product waves (reverse decay). All wavenumbers in the forward decay are similar and hence this decay is local in wavenumber space. On the contrary, the reverse decay generates waves with wavenumbers that are much larger than in the original pump waves and is therefore intrinsically nonlocal. In general, the reverse decay is significantly faster than the forward one, suggesting a nonlocal spectral transport induced by oblique sound waves. Even with low-amplitude sound waves the nonlinear interaction rate is larger than the collisionless dissipation rate. Possible applications regarding acoustic waves observed in the solar corona, solar wind, and topside ionosphere are briefly discussed.

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“…It might be possible to find a low velocity electron beam which generates unstable waves for u < 4u Te , but the decay Langmuir wave (''daughter wave'') obtained from these will be strongly Landau damped, implying that the growth rate of the decay instability becomes negligible. Also, the effects connected with plasma inhomogeneity have been largely ignored, although a consistent treatment of the ionospheric plasma density gradient can bring new understanding of the observational results [Kontar and Pécseli, 2005].…”

Section: Introductionmentioning

confidence: 99%

Nonlinearly generated plasma waves as a model for enhanced ion acoustic lines in the ionosphere

Daldorff¹,

Pécseli²,

Trulsen³

2007

Geophysical Research Letters

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Observations from the EISCAT Svalbard Radar, for instance, demonstrate that the symmetry of the naturally occurring ion line can be broken by an enhanced, non‐thermal, level of fluctuations, i.e., Naturally Enhanced Ion‐Acoustic Lines (NEIALs). In a significant number of cases, the entire ion spectrum can be distorted, with the appearance of a third line, corresponding to a propagation velocity significantly below the ion acoustic sound speed. By numerical simulations, we consider one possible model accounting for the observations, suggesting that a primary process can be electron acoustic waves excited by a cold electron beam. Subsequently, an oscillating two‐stream instability excites electron plasma waves which in turn decay to asymmetric ion lines. Our code solves the full Vlasov equation for electrons and ions, with the dynamics coupled through the electrostatic field derived from Poisson's equation.

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Nonlinear wave interactions as a model for naturally enhanced ion acoustic lines in the ionosphere

Cited by 12 publications

References 20 publications

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

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

Nonlocal nonlinear coupling of kinetic sound waves

Nonlinearly generated plasma waves as a model for enhanced ion acoustic lines in the ionosphere

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