Waves in a moving medium with finite conductivity

Solutions for the steady-state behavior of TEM, TE, and TM waves in an infinite conducting medium moving at a uniform velocity are presented, along with relations between the time average power transmitted through the medium, power dissipated in the medium, and power delivered to an external mechanical load that maintains the medium at a constant velocity. Exact solutions valid at any velocity are obtained using the Lorentz transformation. It is shown that the TEM and TE modes describe relativistic linear induction motors or ac MHD generators in which the usual J × B force is the dominant force mechanism. The TM mode describes a class of electroconvection devices in which the electric field acting on the induced surface charge on the interface between the medium and the air gap is the dominant force mechanism. Both the TE and the TM modes are shown to have efficiencies and force generation capabilities which are independent of the absolute value of velocity.