Higher-Temperature Limit for Turbulent Heating of Plasma by a Cross-Field Current

In theoretical and experimental studies of high-frequency (${\omega }_{\mathrm{ci}}\ll \omega \lesssim {\omega }_{\mathrm{pi}}$) ion heating by electrostatic instabilities driven by a current perpendicular to both a density gradient and an external magnetic field, one instability is found to remain active for a current velocity smaller than the ion thermal velocity. For one experiment, the level of turbulence, effective ion collision frequency, and ion heating rate are also estimated.