Space plasmas usually contain many ion species; moreover, each ion species has many different ionic charge states. The plasmas thus have numerous different ion cyclotron frequencies. Recently, it has been shown that in such multi-ion-species plasmas, new dissipation mechanisms work on the waves propagating perpendicular to the ambient magnetic field [1,2].
We here consider perpendicular magnetosonic waves. First, we numerically calculate power spectra of magnetic field fluctuations and autocorrelation functions in thermal equilibrium plasmas. In a single-ion-species plasma, the autocorrelation function is not damped, because the wave with ω≈kv_A is the only mode. In a multi-ion-species plasma, besides this mode, numerous waves are excited near ion cyclotron frequencies. Then, the autocorrelation function of the quasi-mode consisting of these waves can be strongly damped owing to phase mixing of these waves. This damping is also demonstrated by means of a two-dimensional, electromagnetic, particle code.
Next, with particle simulations, we study the evolution of a macroscopic perpendicular disturbance which we initially excite. It is observed that in a multi-ion-species plasma, this disturbance is damped, which leads to the rise in the heavy-ion temperatures.

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