Phase mixing of nonlinear plasma oscillations in an arbitrary mass ratio cold plasma

Abstract

Nonlinear plasma oscillations in an arbitrary mass ratio cold plasma have been studied using 1D particle-in-cell simulation. In contrast to earlier work for infinitely massive ion plasmas it has been found that the oscillations phase mix away at any amplitude and that the rate at which phase mixing occurs depends on the mass ratio ( Δ = m_-/m₊) and the amplitude. A perturbation theoretic calculation carried up to third order predicts that the normalized phase mixing time ω_p-t_mix depends on the amplitude A and the mass ratio ω as ~[(A²/24)(Δ√1+Δ)]-^1/3. We have confirmed this scaling in our simulations. These cold plasma results may have direct relevance to recent experiments on superintense laser beam plasma interactions with applications to particle acceleration, fast ignitor concept, etc.