We present measurements of the three-dimensional structure of shear Alfven wave currents near the ion-cyclotron frequency. The waves are launched by modulating an electron current filament with transverse size on the order of the electron collisionless skin depth. The component of the current parallel to the background magnetic field is carried by the electrons, while the cross-field current comprises both the ion-polarization and E x B currents.

Experiments are performed in the Large Plasma Device

We report on observations of shear Alfven waves radiated from a source of small transverse size, and the subsequent radial confinement of wave magnetic field energy within a cylindrical plasma. The radius of confinement lies between the kinetic regime of the bulk plasma and the inertial regime at the plasma edge; this radius is found to be a function of wave frequency. Numerical calculations using kinetic theory predict a zero in the perpendicular group velocity at a radius which varies in accord with the observations. An analytic expression for the perpendicular group velocity (valid for small perpendicular wave numbers) is given in the vicinity of the zero crossing.

We report on observations of shear Alfven waves radiated from a source of small transverse size, and the subsequent radial confinement of wave magnetic field energy within a cylindrical plasma. The radius of confinement lies between the kinetic regime of the bulk plasma and the inertial regime at the plasma edge; this radius is found to be a function of wave frequency. Numerical calculations using kinetic theory predict a zero in the perpendicular group velocity at a radius which varies in accord with the observations. An analytic expression for the perpendicular group velocity (valid for small perpendicular wave numbers) is given in the vicinity of the zero crossing.