Production of Alfvén waves by a rapidly expanding dense plasma

The expansion of a dense (initially, n(lpp)/n(0)>>1) laser-produced plasma into an ambient magnetized plasma ( n(0) = 2 x 10(12) cm(-3)) capable of supporting Alfvén waves has been studied. The interaction results in the production of shear Alfvén waves as well as large density perturbations (Delta n/n(0) approximately 0.3) associated with the moving dense plasma. The waves propagate away from the target and are observed to become plasma-column resonances. Spatial patterns of the wave magnetic fields are measured and are used to estimate the coupling efficiency of the laser energy and the kinetic energy of the dense plasma into wave energy.