Turbulence in the (Cold) Interstellar Medium

Séminaire IPAG de Pierre Hily-Blant (IPAG), jeudi 24 mars 2011 à 11h00, IPAG seminar room

The Interstellar Medium is the medium between the stars, yet, it is the place of birth of the stars. At the Galactic scale, the ISM is best understood as a turbulent place. On smaller scales, the cold ISM, where stars form, is likely also turbulent. Words of caution arise from the lack of a definitive proof for the turbulent nature of the ISM. Not only is the ISM turbulent : magnetic fields are now estimated strong enough to imprint their configuration on the cold matter distribution. If a theory of turbulence is still lacking, a theory of compressible, magnetized turbulence may seem unachievable. Even though, understanding turbulence in the cold ISM is required for a proper understanding of the cycle of matter in the ISM. The last decade has fostered direct numerical simulations of the physics of the ISM. Comparisons between theoretical predictions, numerical results, and observational constraints is becoming a tool to study the complex interplay of physics and chemistry in the ISM. I will present the general arguments that support a turbulent view of the ISM, with special emphasis towards the cold ISM. Some consequences of turbulence in the ISM will be presented in the view of recent Herschel satellite results, whereas the Planck mission will provide constraints to the interplay between turbulence and magnetic fields. The soon-opening (extremely) high angular resolution era will certainly bring new constraints on fundamental questions regarding the nature of the interstellar turbulence and the structure of the ISM.