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Low-Mach-number turbulence in interstellar gas revealed by radio polarization gradients
Citation
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 Statement
Copyright © 2011 Nature Publishing Group
Abstract
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 |
|---|---|
| Keywords: | astronomy |
| 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 |
| Downloads: | 0 |
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