Cross-Field Ion-Acoustic Instability Observed in a Turbulent-Heating Experiment

A high-frequency (${\omega }_{\mathrm{ci}}\ll \omega \simeq {\omega }_{\mathrm{pi}}$) electrostatic instability observed in a toroidal turbulent-heating device has been interpreted in terms of ion-acoustic waves excited by a radial, electron temperature gradient across a toroidal magnetic field. The waves have been found to propagate across the field, in the direction opposite to the electron diamagnetic velocity. Observed anomalous electron thermal transport has been explained by the instability.