Nonlinear excitation of electrostatic and magnetostatic zero-frequency modes by finite-amplitude lower-hybrid waves is considered. It is found that modulational instabilities can give rise to enhanced plasma vortices. Dispersion relations, as well as analytical expressions for the growth rates, are obtained. The enhanced vortices may cause anomalous cross-field diffusion which can affect plasma confinement in tokamak devices when lower-hybrid waves are used for plasma heating or current drive. We found that magnetic fluctuations associated with the parametrically driven magnetostatic mode are of particular importance in tokamak plasmas.
Lower-hybrid counter current drive for edge current density modification in DIII-D