Interplay between Alfvén and magnetosonic waves in compressible magnetohydrodynamics turbulence

NAHUEL ANDRÉS; PATRICIO CLARK DI LEONI; PABLO MININNI; PABLO DMITRUK; FOUAD SAHRAOUI; WILLIAM MATTHAEUS

PHYSICS OF PLASMAS

AMER INST PHYSICS

Lugar: New York; Año: 2017 vol. 24

1070-664X

Using spatio-temporal spectra we show direct evidence of excitation of magnetosonic and Alfvén waves in three-dimensional compressible magnetohydrodynamic turbulence at small Mach numbers. For the plasma pressure dominated regime, or high β regime (with β the ratio between fluid and magnetic pressure), and for the magnetic pressure dominated regime, or low β regime, we study magnetic field fluctuations parallel and perpendicular to a guide magnetic field B0 . In the low βcase we find excitation of compressible and incompressible fluctuations, with a transfer of energy towards Alfvénic 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 β case, fast and slow magnetosonic waves are present, with no clear trace of Alfvén waves, and a significant part of the energy is carried by two-dimensional turbulent eddies.