Three-dimensional electromagnetic strong turbulence. I. Scalings, spectra, and field statistics

The first fully three-dimensional (3D) simulations of large-scale electromagnetic strong turbulence (EMST) are performed by numerically solving the electromagnetic Zakharov equations for electron thermal speeds upsilon(e) with upsilon(e)/c >= 0.025. The results of these simulations are presented, focusing on scaling behavior, energy density spectra, and field statistics of the Langmuir (longitudinal) and transverse components of the electric fields during steady-state strong turbulence, where multiple wave packets collapse simultaneously and the system is approximately statistically steady in time. It is shown that for upsilon(e)/c less than or similar to 0.17 strong turbulence is approximately electrostatic and can be explained using the electrostatic two-component model. For upsilon(e)/c greater than or similar to 0.17 the power-law behaviors of the scalings, spectra, and field statistics differ from the electrostatic predictions and results because upsilon(e)/c is sufficiently high to allow transverse modes to become trapped in density wells. The results are compared with those of past 3D electrostatic strong turbulence (ESST) simulations and 2D EMST simulations. For number density perturbations, the scaling behavior, spectra, and field statistics are shown to be only weakly dependent on upsilon(e)/c, whereas the Langmuir and transverse scalings, spectra, and field statistics are shown to be strongly dependent on upsilon(e)/c. Three-dimensional EMST is shown to have features in common with 2D EMST, such as a two-component structure and trapping of transverse modes which are dependent on upsilon(e)/c. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3592147]