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 $v_{e}$ with $v_{e}/c \geq 0.025$. 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 $v_{e}/c < 0.17$ strong turbulence is approximately electrostatic and can be explained using the electrostatic two-component model. For $v_{e}/c > 0.17$ the power-law behaviors of the scalings, spectra, and field statistics differ from the electrostatic predictions and results because $v_{e}/c$ is sufficiently high to allow transverse modes to become trapped in density wells. Three-dimensional EMST is shown to have features in common with 2D EMST, such as a two-component structure and trapping of transverse modes.