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Low-Mach-number turbulence in interstellar gas revealed by radio polarization gradients


Gaensler, BM and Haverkorn, M and Burkhart, B and Newton-McGee, KJ and Ekers, RD and Lazarian, A and McClure-Griffiths, NM and Robishaw, T and Dickey, JM and Green, AJ, Low-Mach-number turbulence in interstellar gas revealed by radio polarization gradients, Nature, 478, (7368) pp. 214-217. ISSN 0028-0836 (2011) [Refereed Article]

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Copyright © 2011 Nature Publishing Group

DOI: doi:10.1038/nature10446


The interstellar medium of the Milky Way is multiphase1, magnetized2 and turbulent3. Turbulence in the interstellar medium produces a global cascade of random gas motions, spanning scales ranging from 100 parsecs to 1,000 kilometres (ref. 4). Fundamental parameters of interstellar turbulence such as the sonic Mach number (the speed of sound) have been difficult to determine, because observations have lacked the sensitivity and resolution to image the small-scale structure associated with turbulent motion5, 6, 7. Observations of linear polarization and Faraday rotation in radio emission from the Milky Way have identified unusual polarized structures that often have no counterparts in the total radiation intensity or at other wavelengths8, 9, 10, 11, 12, and whose physical significance has been unclear13, 14, 15. Here we report that the gradient of the Stokes vector (Q, U), where Q and U are parameters describing the polarization state of radiation, provides an image of magnetized turbulence in diffuse, ionized gas, manifested as a complex filamentary web of discontinuities in gas density and magnetic field. Through comparison with simulations, we demonstrate that turbulence in the warm, ionized medium has a relatively low sonic Mach number, Ms ≲ 2. The development of statistical tools for the analysis of polarization gradients will allow accurate determinations of the Mach number, Reynolds number and magnetic field strength in interstellar turbulence over a wide range of conditions.

Item Details

Item Type:Refereed Article
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Galactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Dickey, JM (Professor John Dickey)
ID Code:75685
Year Published:2011
Web of Science® Times Cited:124
Deposited By:Mathematics and Physics
Deposited On:2012-02-09
Last Modified:2017-10-30

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