Electrostatic instabilities driven by velocity gradients

It is shown that cross-field gradients of guiding-center drift velocities can excite several high-frequency (ω > ωci ) electrostatic instabilities. The instabilities can enhance effective interelectron and/or electron-ion collisions which in turn destory the velocity gradients. In pulsed, turbulent heating experiments, this effect is expected to appear as anomalously rapid current penetration (anomalous skin effect).