Quasi-Linear Dynamics of a Hot Maxwellian Electron Distribution Released from a Localized Region in a Homogeneous Plasma

Abstract

To investigate by numerical analysis the transition towards the asymptotic regime postulated by Ryutov and Sagdeev (1970) in their study of the expansion of a hot electron cloud through a plasma, a physically consistent system of one-dimensional quasi-linear equations has been solved on a Cyber 7600. The results obtained for various conditions of injection were all found in qualitative agreement with the simple analytic description of Ryutov and Sagdeev, in spite of the serious deficiencies of their analysis. Although the aims and techniques of the present study are quite distinct from published numerical works by Takakura and Shibahashi (1976) and Magelssen (1976), all the results point towards the same conclusion: plasmon emission, due to advective instability at the front of the electronic disturbance, is followed by strong reabsorption through a reverse advective process at the rear. In the present note, only the case of a localized hot electronic distribution (initially Maxwellian with Te = 108 K) is considered. The effect of plasmon-plasmon scattering, which can also be included in the programmes, is mentioned in the conclusion.