LABORATORY EXPERIMENTS ON SHEAR ALFVEN WAVES AND THEIR RELATIONSHIP TO SPACE PLASMAS

Alfven waves are ubiquitous in space plasmas and are the means by whic h information about changing currents and magnetic fields are communic ated. Shear Alfven waves radiated from sources with cross-field scale size of the order of the electron inertial length, delta = c/omega(pe) , have properties which differ considerably from planar magnetohydrody namic waves. Currents of cross-field size, delta, are common in space plasmas. A series of experiments in the Large Plasma Device at the Uni versity of California, Los Angeles is presented which illustrates that waves generated by small-scale fluctuating currents have a parallel e lectric field and radiate across magnetic field lines. Data and theory are presented for varying plasma collisionality and ratio of Alfven s peed to electron thermal velocity. Waves generated by two sources are observed to constructively interfere to produce large magnetic fields in spatial regions away from source field lines. The shear Alfven wave is important in the Earth's auroral regions and may play a role in au roral dynamics.