The turbulence driving parameter of molecular clouds in disc galaxies

摘要: Supersonic turbulence plays a pivotal role during the formation of molecular clouds and stars in galaxies. However, little is known about how fraction compressive solenoidal modes velocity field evolves over time it depends on properties cloud or galactic environment. In this work, we carry out magnetohydrodynamical simulations disc galaxies study evolution driving parameter for an ensemble clouds. We find that time-averaged insensitive to position within galaxy. The ensemble-averaged found be rather with $b\sim0.5-0.7$, indicating almost time-independent global star properties. each individual shows highly fluctuating parameter, which would strongly affect cloud's rate. mode can rapidly change only few Myr, both from vice versa. attribute these changes collisions tidal interactions overdensities Last, no significant differences average between hydrodynamic initially magnetised magnetic tends reduce overall fluctuation parameter. as well its uncertainty are seen agreement recent constraints solar neighbourhood