DISINTEGRATION OF ION BANANA ORBITS IN TOKAMAK EDGE PLASMAS

The orbits of ions and electrons in toroidal edge plasmas in the prese nce of low frequency turbulence are investigated. It is found that at low fluctuation levels, ion banana orbits are washed out by turbulent waves and that transport becomes ambipolar. The effective radial step sizes of ions and electrons are comparable. Thus the ion orbit loss me chanism may become ineffective in driving poloidal rotation at the L-H transition in tokamaks.