Stationary incompressible MHD perturbations generated by a current source in a moving plasma

We consider the inductive interaction between a conducting body and a magne tized incompressible plasma in relative uniform motion, which has applicati on to the Io-Jupiter system, for example. An incompressible plasma only sup ports one mode of propagation, namely the Alfven mode. In the case of free oscillations, this mode propagates the perturbations in the magnetic field and in the plasma velocity unattenuated along the direction of the backgrou nd field, while the plasma pressure balances the magnetic pressure The situ ation changes in the presence of source currents and in a flowing plasma. I n particular, the parallel plasma vorticity and parallel plasma current are propagated unattenuated along the familiar Alfven characteristics, while t he field and velocity perturbations suffer Laplacian decay in the near fiel d. We study these perturbations in the frame of the body and compare them t o the case of no source terms. (C) 1999 Elsevier Science Ltd. All rights re served.