Measurement and instability analysis of three-dimensional anisotropic electron distribution functions.

Abstract

A velocity analyzer with high angular resolution ($\frac{d\ensuremath{\Omega}}{4\ensuremath{\pi}}={10}^{\ensuremath{-}4}$) has been used to measure the electron distribution function $f(v, \ensuremath{\theta}, \ensuremath{\varphi})$ in a neutral sheet of a large laboratory plasma. Contours of $f(\mathrm{v})=\mathrm{const}$ form surfaces in velocity space. As $f(\mathrm{v})$ decreases, anisotropic tails form detached surfaces which send filaments out toward the main body. The highly anisotropic structures occur at the Doppler-shifted phase velocity of observed whistler-wave turbulence. Instability analysis of $f(\mathrm{v})$ is consistent with the observed whistler- and Langmuir-wave turbulence.