Launched Waves on a Beam-Plasma System

DeNeef, C. P.; Malmberg, J. H.; O’Neil, T. M.

doi:10.1103/physrevlett.30.1032

Cited by 23 publications

(11 citation statements)

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“…The single-mode solution [3] grows exponentially at small amplitude and with the terminal bubble velocity at large amplitude. As was done successfully in the beam-plasma instability [60,61], the single-mode solution is attributed to the root-mean-square (rms) amplitude of a multimode bubble wave packet [51] but with an evolving dominant wavelength [3] for the RT instability.…”

Section: Basic Modelmentioning

confidence: 99%

“…As a result, nonlinear saturation occurs when the root-meansquare (rms) amplitude of the wave packet is comparable to its average wavelength and the saturation amplitude of the individual components are reduced by a phase-space factor to h k ϳ 1/k 2 L in three dimensions (3D), where L is the system width. Such a suppression in a multimode system was observed directly in the beam-plasma instability [60,61]. More importantly, the rms amplitude of the multimode wave packet was found to evolve into the nonlinear regime just like a single mode until the beam electrons resolved the spectral width.…”

Section: Introductionmentioning

confidence: 96%

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Dependence of turbulent Rayleigh-Taylor instability on initial perturbations

Dimonte

2004

Phys. Rev. E

109

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The dependency of the self-similar Rayleigh-Taylor bubble acceleration constant alpha(b)(identical with [(amplitude)/2] x (displacement) x (Atwood number)) on the initial perturbation amplitude h(0k) is described with a model in which the exponential growth of a small amplitude packet of modes makes a continuous nonlinear transition to its "terminal" bubble velocity proportional, variant Fr[equal to(Froude number)(1/2)]. Then, by applying self-similarity (diameter proportional, variant amplitude), alpha(b) is found to increase proportional to Fr and logarithmically with h(0k). The model has two free parameters that are determined from experiments and simulations. The augmentation of long wavelength perturbations by mode coupling is also evaluated. This is found to decrease the sensitivity of alpha(b) on the initial perturbations when they are smaller than the saturation amplitude of the most unstable modes. These results show that alpha(b) can vary by a factor of 2-3 with initial conditions in reasonable agreement with experiments and simulations.

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Section: Basic Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Dependence of turbulent Rayleigh-Taylor instability on initial perturbations

Dimonte

2004

Phys. Rev. E

109

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“…Correspondingly, in the linear region of the beam plasma instability (before the beam is trapped), a launched unstable wave has no effect on the exponentially growing noise modes. 7 Once the nonlinear term in Eq.…”

Section: (2)mentioning

confidence: 99%

“…This amplitude limiting and the spatial evolution of these limited waves have been previously calculated by regarding them as a slow modulation of the launched wave's amplitude and phase. 7 It is likely that the failure is not the fault of the Van der Pol model, but rather is a result of the constant-driver approximation that facilitated the calculation.…”

Section: (2)mentioning

confidence: 99%

“…We find qualitative agreement with recently published results on the amplitude limiting of unstable waves at the neighboring frequencies of a launched wave that traps the electron beam. 7 When a low-density, cold electron beam is injected into a collisionless, Maxwellian plasma along a strong magnetic field, unstable waves in a narrow frequency band grow exponentially in space, starting from the thermally generated noise level. The growth continues at the rate predicted by linear theory until the fastest-growing-wave's amplitude is sufficient to trap the beam electrons.…”

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confidence: 99%

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