Three-dimensional electromagnetic strong turbulence: Dependence of the statistics and dynamics of strong turbulence on the electron to ion temperature ratio

Graham, D. B.; Cairns, Iver H.; Skjaeraasen, O.; Robinson, P. A.

doi:doi:10.1063/1.3684672

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Kinetic cascade beyond magnetohydrodynamics of solar wind turbulence in two-dimensional hybrid simulations

The nature of solar wind turbulence in the dissipation range at scales much smaller than the large magnetohydrodynamic (MHD) scales remains under debate. Here, a two-dimensional model based on the hybrid code abbreviated as A.I.K.E.F. is presented, which treats massive ions as particles obeying the kinetic Vlasov equation and massless electrons as a neutralizing fluid. Up to a certain wavenumber in the MHD regime, the numerical system is initialized by assuming a superposition of isotropic Alfv...

Effects of dust particles on the dynamics of blobs in the scrape off layer II

A detailed analysis is performed of the results of numerical simulations of the dynamics of plasma blobs, obtained within the model of the nonlinear interchange mode, including the effects of the dissipation by dust, in tokamak scrape-off layer plasmas. The maximum distances that a plasma blob may travel in the radial direction are calculated under physical conditions characteristic for several large tokamaks that are presently in operation, and it is found that a relatively small amount of 30 ...

The temperature ratio T_i/T_e of ions to electrons affects both the ion-damping rate and the ion-acoustic speed in plasmas. The effects of changing the ion-damping rate and ion-acoustic speed are investigated for electrostatic strong turbulence and electromagnetic strong turbulence in three dimensions. When ion damping is strong, density wells relax in place and act as nucleation sites for the formation of new wave packets. In this case, the density perturbations are primarily density wells supported by the ponderomotive force. For weak ion damping, corresponding to low T_i/T_e, ion-acoustic waves are launched radially outwards when wave packets dissipate at burnout, thereby increasing the level of density perturbations in the system and thus raising the level of scattering of Langmuir waves off density perturbations. Density wells no longer relax in place so renucleation at recent collapse sites no longer occurs, instead wave packets form in background low density regions, such as superpositions of troughs of propagating ion-acoustic waves. This transition is found to occur at T_i/T_e ≈ 0.1. The change in behavior with T_i/T_e is shown to change the bulk statistical properties, scaling behavior, spectra, and field statistics of strong turbulence. For T_i/T_e>rsim0.1, the electrostatic results approach the predictions of the two-component model of Robinson and Newman, and good agreement is found for T_i/T_e>rsim0.15.

Article Outline

INTRODUCTION
ZAKHAROV EQUATIONS
QUALITATIVE FEATURES OF STRONG TURBULENCE
1. Mean energy density
2. Maximum energy densities
3. Density perturbations
4. Number density of wave packets
SCALING BEHAVIOR
1. Energy density scalings
2. Number density scalings
3. Scalings of energy density and number density with ion speed and ion damping
SPECTRA
1. ESST
2. EMST
FIELD-STRENGTH STATISTICS
1. ESST
2. EMST
DISCUSSION AND SUMMARY

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KEYWORDS and PACS

Keywords

nucleation, plasma density, plasma ion acoustic waves, plasma Langmuir waves, plasma nonlinear processes, plasma simulation, plasma temperature, plasma turbulence

PACS

52.35.Ra

Plasma turbulence
52.65.-y

Plasma simulation
52.35.Mw

Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Fp

Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.25.-b

Plasma properties

ARTICLE DATA

Digital Object Identifier

http://dx.doi.org/10.1063/1.3684672

PUBLICATION DATA

ISSN

1070-664X (print)

1089-7674 (online)

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American Institute of Physics

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