There are many situations of interest in space and astrophysics which consist of a conducting body moving through a magnetized plasma. It is well known that large conducting objects which move slowly across magnetic field lines radiate low frequency (Alfv¿n) waves.

In this paper we study the interaction between a plasma and a moving conductor in order to estimate the total power radiated at all frequencies. Toward this end, we develop formalism which permits us to compute the response of the plasma to a external current source. We then derive an integral equation which relates the source current to the electrical properties of the conducting body. Since the integral equation is prohibitively difficult to solve, we estimate the total radiated power for simple geometries using energy conservation and a source current deduced by physical reasoning. We find in general that radiation is produced at all frequencies for which one of the plasma modes has zero phase velocity in some direction.

The mechanism by which this radiation is produced is analogous to Cherenkov radiation. In the cold plasma approximation, in a plasma for which &ohgr;p 2≫&OHgr;e 2 and V2≪cA 2≪c2, there is radiation in three frequency bands: &ohgr;<&OHgr;i, &ohgr;LH<&ohgr;<&OHgr;e, and &ohgr;p<&ohgr;<&ohgr;UH, where V is the speed of the body, cA is the Alfv¿n speed, c is the speed of light in vacuum. &ohgr; is the frequency of the radiation, and &OHgr;i, &ohgr;LH, &OHgr;e, &ohgr;p, &ohgr;UH are the ion cyclotron, lower hybrid, electron cyclotron, plasma, and upper hybrid frequencies, respectively. To gain a better understanding of the properties of the plasma waves in these frequency bands, we present polar plots of the phase and group velocities of these waves. Finally, we present estimates of radiated power for a sphere and for a cylinder of arbitrary size. We find that a wire 10 km long and 1 mm in radius radiates about 40 watts. The Jovian satellite Io, known to be a strong source of waves in the first frequency band, also radiates 2.9¿10-7 times as much power in the second frequency band.