Particle reacceleration in radio galaxies

The magnetohydrodynamic wave spectra expected in a plasma cloud moving through an external gas are derived using the drag of that gas, coupled through surface instabilities, as the energy source and microscopic damping as the energy drain. Using these spectra, the reacceleration rate of relativistic particles is calculated. It turns out that plasma clouds with high initial kinetic energy can reaccelerate the radio synchrotron emitting particles fast enough to overcome synchrotron losses but that the process is inefficient and most of the kinetic energy goes into heating of the background gas.