Speaker
Robertas Aluzas
(School of Physics and Astronomy, University of Leeds)
Description
The interstellar medium (ISM) is highly structured and inhomogeneous. Density enhancements (clouds) that occupy a small volume fraction can dominate the mass fraction. The interaction between clouds and flows is a key process affecting the behaviour and evolution of the ISM, with implications for star formation and galaxy evolution. For instance, dense clouds may be destroyed by a flow, while at other times they may be compressed to the point that star formation is initiated.
Consequently, the physical interaction between a shock and a cloud, has attracted a lot of study, including various multi-physics models. However, very little work yet concerns the presence of multiple clouds and their mutual effect on a flow. I will present new results of numerical simulations of shock interactions with many clouds. The aim of this work is to self-consistently model the evolution of the flow due to the presence of multiple clouds and the evolution of the clouds due to the mass-loaded flow.
In purely hydrodynamic simulations we find that although upstream clouds are effective at slowing down the shock the turbulence and momentum in the mass-loaded flow generally destroys downstream clouds faster. The effect is particularly significant for clouds denser than the average cloud in the distribution.
In MHD simulations the magnetic fields impose structure on the interacting flow. Compared to the purely hydrodynamic case we find that perpendicular and oblique fields lead to clumpiness, while
?flux-ropes? in the parallel case create two distinct downstream regions, which in extreme cases can cause radically different cloud evolution depending on the exact position of downstream clouds.
Author
Robertas Aluzas
(School of Physics and Astronomy, University of Leeds)