Laboratory Studies of Turbulence Associated with Localized Current Layers

Localized current layers are a natural consequence of the interaction of the solar wind with the earth's magnetic field. In particular, field-aligned currents dynamically link the active magnetotail to the auroral ionosphere. Within these currents there may develop small-scale phenomena such as density-gradient or shear-driven instabilities, or electron solitary structures and micro-turbulence which may profoundly influence the larger-scale dynamics of the system. The Basic Plasma Science Facility (BaPSF) at UCLA offers a unique opportunity to model magneto/heliospheric phenomena, including current sheets. We present measurements from laboratory experiments of an electron current sheet which is several ion-gyroradii thick by up to ten Alfv\'{e}n wavelengths along the field(1cm by 20m). The current sheet leads to a depletion of the background plasma, forming a field-aligned density depression. Drift-Alfv\'{e}n waves are spontaneously excited and drive cross-field particle transport which relaxes the density gradient and modulates the current flow. We will also present initial results of small-scale electric field spikes within the current sheet using specially fabricated dipole probes with separation on the order of the Debye length---here 13 microns. These measurements are motivated by the observation of electron solitary structures throughout the magnetosphere.