Langmuir “snakes” and electrostatic decay in the solar wind

Graham, Daniel B.; Cairns, Iver H.; Robinson, P. A.

doi:10.1002/grl.50475

Cited by 10 publications

(15 citation statements)

References 33 publications

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“…In Graham et al [2013], the split spectral peak events were shown to be generally consistent with ES decay. We now compare the observed P S and P L with the weak turbulence predictions for ES decay.…”

Section: One-dimensional Split Spectral Peak Eventsmentioning

confidence: 88%

“…So for large k b , the number of backscatters can be truncated to a small number without a condensate forming [e.g., Robinson et al, 1992;Graham et al, 2013]. So for large k b , the number of backscatters can be truncated to a small number without a condensate forming [e.g., Robinson et al, 1992;Graham et al, 2013].…”

Section: Theorymentioning

confidence: 99%

“…A particular type of event that is difficult to classify are the Langmuir "snake" events analyzed in Graham et al [2013]. An example of a Langmuir snake is shown in Figure 5.…”

Section: Event Classificationmentioning

confidence: 99%

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Dynamical evidence for nonlinear Langmuir wave processes in type III solar radio bursts

Graham

Cairns

2014

JGR Space Physics

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The nonlinear processes and evolution of Langmuir waves in the source regions of type III solar radio bursts are explored in detail. Langmuir waves recorded by the Time Domain Sampler of the STEREO/WAVES instrument can be roughly classified into six groups based on the waveform, power spectra, and field strength perpendicular to the local magnetic field. It is argued that these groups correspond to either different stages of the evolution of Langmuir waves generated by electron beams or differ due to the direction of the magnetic field relative to the solar wind velocity. Approximately half of the observed Langmuir waves have strong perpendicular fields, meaning that understanding how these fields are produced is crucial for understanding type III sources. Most events recorded are either localized waveforms consistent with Langmuir eigenmodes or have two or more spectral peaks consistent with electrostatic (ES) decay of Langmuir/z mode waves. The remaining events appear to correspond to either earlier or later stages of Langmuir wave evolution or are decay events for which the Doppler shift is insufficient to distinguish the beam‐driven and product Langmuir waves. This is supported by the fact that most events exceed the threshold for ES decay even though their spectra show no evidence for decay and some of the events are observed when the solar wind flow is approximately perpendicular to the magnetic field, minimizing Doppler shifting. Low‐frequency fields produced by intense Langmuir waves are quantitatively consistent with density perturbations produced by the ponderomotive force, ion‐acoustic waves produced by ES decay, or sheath rectification. Above the observed nonlinear threshold, quantitative analysis suggests that the observed low‐frequency signals are consistent with perturbations produced by ponderomotive effects and ion‐acoustic waves produced by ES decay, but effects of sheath rectification may also contribute.

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Section: One-dimensional Split Spectral Peak Eventsmentioning

confidence: 88%

Section: Theorymentioning

confidence: 99%

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Dynamical evidence for nonlinear Langmuir wave processes in type III solar radio bursts

Graham

Cairns

2014

JGR Space Physics

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“…Correspondingly, the spectrum of E L parallel to B has a single peak. The angle between B and the solar wind velocity is θ Bv =71°, and the predicted Doppler‐shifted frequency difference is ∼300Hz, so if decay was occurring we expect to see distinct spectral peaks near f p [ Graham et al , ; Graham and Cairns , ].…”

Section: Examples Of Harmonic Wavesmentioning

confidence: 99%

Harmonic waves and sheath rectification in type III solar radio bursts

2014

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In type III solar radio bursts and planetary foreshocks, Langmuir waves are produced by electron beams and converted partially to radio waves by linear and nonlinear processes. Lower amplitude second harmonic electric fields are observed simultaneously during the most intense Langmuir wave events in type III source regions. The electric fields at the harmonic frequencies can arise from various mechanisms, such as radio wave emission by either coalescence or antenna mechanisms, nonlinear currents, harmonics of Langmuir waves, electron trapping in Langmuir wave potentials, and Langmuir wave rectification at the sheath surrounding the spacecraft, or they can result from instrumental harmonics. In this paper the relative powers and electric field vectors of Langmuir waves and the harmonic fields are compared for multiple events. The structure of the harmonic field is shown to be determined by the Langmuir waveform, but the harmonic field direction is typically closely aligned with the solar wind flow. The magnitude, structure, and orientation of the harmonic fields is used to determine which processes are responsible. It is shown that the dominant process generating the observed harmonic fields is Langmuir wave rectification at the sheath surrounding the spacecraft.

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“…Density perturbations play a major role in the processes considered to date, including refraction and scattering of Langmuir waves by density fluctuations [3], stochastic growth effects [4], and also nonlinear wave-wave processes such as electrostatic (ES) decay [5][6][7]. Some Langmuir waves exhibit periodic beating consistent with ES decay [7][8][9][10]. However, Langmuir waves often appear localized with typical length scales of $ð10 2 -10 3 Þ D [11][12][13][14].…”

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confidence: 99%

Constraints on the Formation and Structure of Langmuir Eigenmodes in the Solar Wind

Graham

Cairns

2013

Phys. Rev. Lett.

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Localized Langmuir waves are commonly observed in space plasmas and are a potential source of radio waves. Using electric field data from STEREO, it is shown that these localized Langmuir waves are eigenmodes of density wells estimated independently. An analytic model is developed for the eigenmode frequencies. The inferred depths and widths of the density wells typically only allow the zeroth-order Langmuir eigenmode to form, explaining the preponderance of single-peaked waveforms. More complicated waveforms are shown to be consistent with single eigenmode solutions of more complicated density profiles. The inferred depth of the density well increases with Langmuir wave intensity, consistent with the ponderomotive force but not wave packet collapse.

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Langmuir “snakes” and electrostatic decay in the solar wind

Cited by 10 publications

References 33 publications

Dynamical evidence for nonlinear Langmuir wave processes in type III solar radio bursts

Dynamical evidence for nonlinear Langmuir wave processes in type III solar radio bursts

Harmonic waves and sheath rectification in type III solar radio bursts

Constraints on the Formation and Structure of Langmuir Eigenmodes in the Solar Wind

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