Observation of Self Generated Flows in Tokamak Plasmas With Lower Hybrid Driven Current

In Alcator C-Mod discharges lower hybrid waves have been shown to induce a counter-current change in toroidal rotation of up to 60 km/s in the central region of the plasma (r/a $\sim <$ 0.4). This modification of the toroidal rotation profile develops on a time scale comparable to the current redistribution time ($\sim $100ms) but longer than the energy and momentum confinement times ($\sim $20ms). Comparison of co-and counter-current injected waves indicates that current drive (as opposed to heating) is responsible for the rotation profile modifications. Furthermore, the changes in central rotation velocity induced by lower hybrid current drive (LHCD) are well correlated with changes in normalized internal inductance. The application of LHCD has been shown to generate strongly sheared rotation profiles and a negative increment in the radial electric field profile consistent with a fast electron pinch. Supported by USDoE award DE-FC02-99ER54512.