Mode-analytical Examination of Vortex Dynamics of a Pure Electron Plasma in the Relaxation to a Meta-equilibrium Distribution

Vortex patches of intense density generated by the diocotron instability in a magnetized pure electron plasma merge each other accompanied by the production of filaments and finally relax to a bell shape distribution surrounded by a halo of low‐density electrons. Here we reexamine the vortical dynamics in terms of the time evolution of the power spectrum in the mode‐number space. Triggered by the instability, the initial axisymmetric ring distribution is deformed and torn into mesoscopic blobs, and a distribution of radial flux is generated around the blobs. In the merging process between vortex patches, the energy spectrum expands toward higher mode‐number space, while the dominant mode shifts downward to lower mode numbers as this process proceeds. The turbulent period characterized by the repeated mergers is accompanied by a fast reduction of the enstrophy. During this relaxation the energy and the angular momentum of the whole plasma system remain conserved. In a slow process after the rapid relaxatio...