Interplay between Alfvén and magnetosonic waves in compressible magnetohydrodynamics turbulence

Using spatio-temporal spectra, we show direct evidence of excitation of magnetosonic and Alfven waves in three-dimensional compressible magnetohydrodynamic turbulence at small Mach numbers. For the plasma pressure dominated regime, or the high beta regime (with beta the ratio between fluid and magnetic pressure), and for the magnetic pressure dominated regime, or the low beta regime, we study magnetic field fluctuations parallel and perpendicular to a guide magnetic field B-0. In the low beta case, we find excitation of compressible and incompressible fluctuations, with a transfer of energy towards Alfvenic modes and to a lesser extent towards magnetosonic modes. In particular, we find signatures of the presence of fast magnetosonic waves in a scenario compatible with that of weak turbulence. In the high beta case, fast and slow magnetosonic waves are present, with no clear trace of Alfven waves, and a significant part of the energy is carried by two-dimensional turbulent eddies. Published by AIP Publishing.