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Astron. Astrophys. 362, 333-341 (2000)

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The distribution of shock waves in driven supersonic turbulence

M.D. Smith 1, M.-M. Mac Low 2 and F. Heitsch 3

1 Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland, UK (mds@star.arm.ac.uk)
2 Department of Astrophysics, American Museum of Natural History, 79th St. at Central Park West, New York, NY 10024-5192, USA (mordecai@amnh.org)
3 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany (heitsch@mpia-hd.mpg.de)

Received 15 May 2000 / Accepted 3 August 2000


Supersonic turbulence generates distributions of shock waves. Here, we analyse the shock waves in three-dimensional numerical simulations of uniformly driven supersonic turbulence, with and without magnetohydrodynamics and self-gravity. We can identify the nature of the turbulence by measuring the distribution of the shock strengths.

We find that uniformly driven turbulence possesses a power law distribution of fast shocks with the number of shocks inversely proportional to the square root of the shock jump speed. A tail of high speed shocks steeper than Gaussian results from the random superposition of driving waves which decay rapidly. The energy is dissipated by a small range of fast shocks. These results contrast with the exponential distribution and slow shock dissipation associated with decaying turbulence.

A strong magnetic field enhances the shock number transverse to the field direction at the expense of parallel shocks. A simulation with self-gravity demonstrates the development of a number of highly dissipative accretion shocks. Finally, we examine the dynamics to demonstrate how the power-law behaviour arises.

Key words: hydrodynamics – shock waves – turbulence – ISM: clouds – ISM: kinematics and dynamics

Send offprint requests to: M.D. Smith

© European Southern Observatory (ESO) 2000

Online publication: October 30, 19100