Evolution of the bump-on-tail instability in compressing plasma

Through particle-in-cell simulations, the evolution of the bump-on-tail instability (BoTI) is studied for plasma subject to one-dimensional mechanical compression. It is shown that the final state of BoTI differs from that described by quasilinear theory for stationary bulk plasma and can depend on the compression history. The transformation of thermal energy into wave energy increases the plasma compressibility, thereby decreasing the amount of mechanical work required to compress the plasma to a specified size. Also, the energy spectrum of the excited modes can be tailored by choosing a particular compression scenario, offering a new technique for manipulating plasmas mechanically.