Nonlinear Langmuir waves during Type III solar radio bursts

Nicholson, D. R.; Goldman, M. V.; Hoyng, P.; Weatherall, James C.

doi:10.1086/156296

Cited by 126 publications

(49 citation statements)

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“…This threshold value is comparable to the observed values of W L n e T e of ∼2×10 −5 and 8×10 −6 (see , Table 1). These observations are consistent with the theoretical and computational results for the evolution of beam excited Langmuir waves Nicholson et al, 1978). As far as the recent hypotheses of Langmuir collapse based on the localized Langmuir eigenstates in the ocean of plane waves as seen in numerical simulations are concerned (Robinson, 1997), there is no observational evidence for structures with f <f pe .…”

Section: Discussionsupporting

confidence: 86%

“…The intense interest in this topic is not only because of the fundamental nature of the problem (Zakharov, 1972), but also because of its practical importance in laser heating of pellets (Montgomery et al, 1999), ionospheric modification experiments (DuBois et al, 1993), solar radio astronomy (Papadopoulos et al, 1974;Smith et al, 1979;Goldstein et al, 1979;Goldman and Nicholson , 1978;Nicholson et al, 1978) and other astrophysical applications (Pelletier et al, 1988). For example, in the case of solar type III radio bursts, Langmuir collapse and related nonlinear processes are believed to play an important role in stabilization of the electron beams, and the conversion of Langmuir waves into the fundamental and second harmonic radio waves.…”

Section: Introductionmentioning

confidence: 99%

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High frequency ion sound waves associated with Langmuir waves in type III radio burst source regions

Thejappa

MacDowall

2004

Nonlin. Processes Geophys.

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Abstract. Short wavelength ion sound waves (2-4 kHz) are detected in association with the Langmuir waves (∼15-30 kHz) in the source regions of several local type III radio bursts. They are most probably not due to any resonant wavewave interactions such as the electrostatic decay instability because their wavelengths are much shorter than those of Langmuir waves. The Langmuir waves occur as coherent field structures with peak intensities exceeding the Langmuir collapse thresholds. Their scale sizes are of the order of the wavelength of an ion sound wave. These Langmuir wave field characteristics indicate that the observed short wavelength ion sound waves are most probably generated during the thermalization of the burnt-out cavitons left behind by the Langmuir collapse. Moreover, the peak intensities of the observed short wavelength ion sound waves are comparable to the expected intensities of those ion sound waves radiated by the burnt-out cavitons. However, the speeds of the electron beams derived from the frequency drift of type III radio bursts are too slow to satisfy the needed adiabatic ion approximation. Therefore, some non-linear process such as the induced scattering on thermal ions most probably pumps the beam excited Langmuir waves towards the lower wavenumbers, where the adiabatic ion approximation is justified.

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Section: Discussionsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

High frequency ion sound waves associated with Langmuir waves in type III radio burst source regions

Thejappa

MacDowall

2004

Nonlin. Processes Geophys.

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“…It is suggested (Kaplan and Tsytovich, 1968) that the induced scattering by thermal ions when T e = T i , which acts as the electrostatic decay (ESD) of the Langmuir waves (L) into daughter Langmuir (L ) and ion sound (S) waves when T e > T i , can stabilize the beam by scattering the Langmuir waves from regions of resonance toward lower wave numbers (T e and T i are the electron and ion temperatures, respectively). However, since the intensities of the beam-excited Langmuir waves in type III bursts are expected to be well above the threshold for the strong turbulence processes, the weak turbulence processes are argued to be not as efficient as OTSI (Papadopoulos et al, 1974;Smith et al, 1979) and related spatial collapse (Nicholson et al, 1978;Goldman et al, 1980), which can stabilize the beam by pumping the Langmuir waves from the resonance regions toward higher wave numbers.…”

Section: Published By Copernicus Publications On Behalf Of the Europementioning

confidence: 99%

Evidence for four- and three-wave interactions in solar type III radio emissions

2013

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The high time resolution observations obtained by the STEREO/WAVES experiment show that in the source regions of solar type III radio bursts, Langmuir waves often occur as intense localized wave packets with short durations of only few ms. One of these wave packets shows that it is a three-dimensional field structure with W_Ln_eT_e ~ 10⁻³, where W_L is the peak energy density, and n_e and T_e are the electron density and temperature, respectively. For this wave packet, the conditions of the oscillating two-stream instability (OTSI) and supersonic collapse are satisfied within the error range of determination of main parameters. The density cavity, observed during this wave packet indicates that its depth, width and temporal coincidence are consistent with those of a caviton, generated by the ponderomotive force of the collapsing wave packet. The spectrum of each of the parallel and perpendicular components of the wave packet contains a primary peak at f_pe, two secondary peaks at f_pe ± f_S and a low-frequency enhancement below f_S, which, as indicated by the frequency and wave number resonance conditions, and the fast Fourier transform (FFT)-based tricoherence spectral peak at (f_pe, f_pe, f_pe + f_S, f_pe − f_S), are coupled to each other by the OTSI type of four-wave interaction (f_pe is the local electron plasma frequency and f_S is the frequency of ion sound waves). In addition to the primary peak at f_pe, each of these spectra also contains a peak at 2f_pe, which as indicated by the frequency and wave number resonance conditions, and the wavelet-based bicoherence spectral peak at (f_pe, f_pe), appears to correspond to the second harmonic electromagnetic waves generated as a result of coalescence of oppositely propagating sidebands excited by the OTSI. Thus, these observations for the first time provide combined evidence that (1) the OTSI and related strong turbulence processes play a significant role in the stabilization of the electron beam, (2) the coalescence of the oppositely propagating up- and down-shifted daughter Langmuir waves excited by the OTSI probably is the emission mechanism of the second harmonic radiation, and (3) the Langmuir collapse follows the route of OTSI in some of the type III radio bursts

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“…It is a nonlinear self-focusing (or modulational) process (Zakharov, 1972;Nicholson et al, 1978;Robinson, 1997), in which wave energy refracts into the density depression associated with a wavepacket, intensifies the field and the nonlinear ponderomotive force, which then further evacuates the plasma and causes the wavepacket's scale size to decrease, leading to more refraction and further collapse of the scale size. A wavepacket of a given spatial scale L has a threshold electric field for collapse to occur.…”

Section: Appendix a Conditions For Wave Collapse In The Auroral Ionosmentioning

confidence: 99%

“…The inspiration for this work comes from investigations of Langmuir waves in the electron foreshock, where they are generated by electrons streaming away from the bow shock that develop a beam distribution function by time-of-flight effects. In this region nonlinear processes such as modulational instabilities and strong turbulence wave collapse (for example, Zakharov, 1972;Nicholson et al, 1978;Robinson, 1997) and nonlinear three-wave decay into daughter Langmuir and ion acoustic waves (Cairns and Melrose, 1985;Lin et al, 1986) do not appear to saturate the beam instability because the observed electric fields and predicted beam speeds are typically too low (Cairns and Robinson, 1992;Cairns et al, 1998). From statistics of the Langmuir wave amplitudes measured with the ISEE-1 satellite wave receiver, Robinson (1997, 1999) find that the wave fields follow a log-normal distribution.…”

Section: Introductionmentioning

confidence: 99%

Statistics of auroral Langmuir waves

2008

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Abstract. The Physics of Auroral Zone Electrons II (PHAZE II) sounding rocket was launched in February 1997 into active pre-midnight aurora. The resulting high frequency wave data are dominated by Langmuir waves. Consistent with many previous observations the Langmuir waves are sporadic, occurring in bursts lasting up to a few hundred ms. We compute statistics of the electric field amplitudes of these Langmuir waves, with two results. First, the shape of the distribution of running averages of the electric field amplitudes remains approximately stationary for a large range of widths of running average less than ∼0.3 ms and for a large range of widths exceeding about 1 ms. The interpretation of this transition timescale is unclear but appears unlikely to be of instrumental origin. Second, for 2.6-ms running averages, corresponding to the latter range, the distribution of the logarithm of electric field amplitudes matches a Gaussian form very well for all nine cases studied in detail, hence the statistics are lognormal. These distributions are consistent with stochastic growth theory (SGT).

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Nonlinear Langmuir waves during Type III solar radio bursts

Cited by 126 publications

References 0 publications

High frequency ion sound waves associated with Langmuir waves in type III radio burst source regions

High frequency ion sound waves associated with Langmuir waves in type III radio burst source regions

Evidence for four- and three-wave interactions in solar type III radio emissions

Statistics of auroral Langmuir waves

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