The enhanced effective collision frequency in a turbulent plasma produced by a strong electric field is studied using a small toroidal device. The collision frequency is presented as a function of the electric field E and the average electron drift velocity. Two collision frequency regimes are identified. In the regime/where voc E1/2, the current driven ion-acoustic turbulence is considered responsible. In the regime II where voc E, the runaway electrons are considered to generate ion density fluctuations nonlinearly. The nonlinear model of Papadopoulos with some extensions is successfully applied for explanaton of the regime II. Because this model has been proposed for the illustration of aurora phenomena, the relevance of the present work to space plasma phenomena is discussed. © 1979, Cambridge University Press. All rights reserved.
