Résumé :
The Interstellar Medium is both the medium between the stars and 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 which itself amounts to the lack of a complete theory of turbulence.
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 review the
general arguments that support a turbulent view of the ISM, with
special emphasis towards the cold molecular 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.
