skip to main content

Title: Long-term evolution of decaying magnetohydrodynamic turbulence in the multiphase interstellar medium

Supersonic turbulence in the interstellar medium (ISM) is believed to decay rapidly within a flow crossing time irrespective of the degree of magnetization. However, this general consensus of decaying magnetohydrodynamic (MHD) turbulence relies on local isothermal simulations, which are unable to take into account the roles of the global structures of magnetic fields and the ISM. Utilizing three-dimensional MHD simulations including interstellar cooling and heating, we investigate decaying MHD turbulence within cold neutral medium sheets embedded in a warm neutral medium. The early evolution of turbulent kinetic energy is consistent with previous results for decaying compressible MHD turbulence characterized by rapid energy decay with a power-law form of Eāˆt {sup ā€“1} and by a short decay time compared with the flow crossing time. If initial magnetic fields are strong and perpendicular to the sheet, however, long-term evolution of the kinetic energy shows that a significant amount of turbulent energy (āˆ¼0.2E {sub 0}) still remains even after 10 flow crossing times for models with periodic boundary conditions. The decay rate is also greatly reduced as the field strength increases for such initial and boundary conditions, but not if the boundary conditions are those for a completely isolated sheet. We analyze velocitymore » power spectra of the remaining turbulence to show that in-plane, incompressible motions parallel to the sheet dominate at later times.« less
Authors:
 [1] ;  [2]
  1. Currently at Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)
  2. Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7 (Canada)
Publication Date:
OSTI Identifier:
22341974
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 778; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BOUNDARY CONDITIONS; DECAY; EVOLUTION; INTERSTELLAR SPACE; MAGNETIC FIELDS; MAGNETIZATION; MAGNETOHYDRODYNAMICS; SIMULATION; SPECTRA; THREE-DIMENSIONAL CALCULATIONS; TURBULENCE; VELOCITY