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

Abstract

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 νe with νe/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 νe/c≳0.17 strong turbulence is approximately electrostatic and can be explained using the electrostatic two-component model. For ve/c≳0.17 the power-law behaviors of the scalings, spectra, and field statistics differ from the electrostatic predictions and results because νe/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 νe/c, whereas the Langmuir and transverse scalings, spectra, and field statistics are shown to be strongly dependent on νe/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 νe/c.