The Intermittency of ISM Turbulence: What Do the Observations Tell Us?

Falgarone, É.; Momferratos, Giorgos; Lesaffre, Pierre

doi:10.1007/978-3-662-44625-6_9

Cited by 15 publications

(13 citation statements)

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“…The map of S highlights long, narrow structures of high S that trace abrupt changes of ψ at the interfaces between extended areas within which the polarization angle is ordered. Falgarone et al (2015) found a correlation between the structures in S and large velocity shears in incompressible magnetized turbulence. The structures seen in the Planck data bear a morphological resemblance to features associated with Faraday rotation in gradient maps of polarized synchrotron emission at 1.4 and 2.3 GHz (Gaensler et al 2011;Iacobelli et al 2014), which have been related to fluctuations in the GMF and in the ionized gas density in MHD turbulence (Burkhart et al 2012).…”

Section: Introductionmentioning

confidence: 84%

Planckintermediate results

Aghanim

Alves

Arzoumanian

et al. 2016

A&A

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Using data from the Planck satellite, we study the statistical properties of interstellar dust polarization at high Galactic latitudes around the south pole (b < −60• ). Our aim is to advance the understanding of the magnetized interstellar medium (ISM), and to provide a modelling framework of the polarized dust foreground for use in cosmic microwave background (CMB) component-separation procedures. We examine the Stokes I, Q, and U maps at 353 GHz, and particularly the statistical distribution of the polarization fraction (p) and angle (ψ), in order to characterize the ordered and turbulent components of the Galactic magnetic field (GMF) in the solar neighbourhood. The Q and U maps show patterns at large angular scales, which we relate to the mean orientation of the GMF towards Galactic coordinates (l 0 , b 0 ) = (70The histogram of the observed p values shows a wide dispersion up to 25%. The histogram of ψ has a standard deviation of 12• about the regular pattern expected from the ordered GMF. We build a phenomenological model that connects the distributions of p and ψ to a statistical description of the turbulent component of the GMF, assuming a uniform effective polarization fraction (p 0 ) of dust emission. To compute the Stokes parameters, we approximate the integration along the line of sight (LOS) as a sum over a set of N independent polarization layers, in each of which the turbulent component of the GMF is obtained from Gaussian realizations of a power-law power spectrum. We are able to reproduce the observed p and ψ distributions using a p 0 value of 26%, a ratio of 0.9 between the strengths of the turbulent and mean components of the GMF, and a small value of N. The mean value of p (inferred from the fit of the large-scale patterns in the Stokes maps) is 12 ± 1%. We relate the polarization layers to the density structure and to the correlation length of the GMF along the LOS. We emphasize the simplicity of our model (involving only a few parameters), which can be easily computed on the celestial sphere to produce simulated maps of dust polarization. Our work is an important step towards a model that can be used to assess the accuracy of component-separation methods in present and future CMB experiments designed to search the B mode CMB polarization from primordial gravity waves.Key words. magnetohydrodynamics (MHD) -polarization -methods: data analysis -dust, extinction -cosmic background radiation -ISM: magnetic fields IntroductionInterstellar magnetic fields are tied to the interstellar gas. Together with cosmic rays they form a dynamical system that Corresponding author: A. Bracco, e-mail: andrea.bracco@cea.fr is an important (but debated) facet of the physics of galaxies. Magnetic fields play a pivotal role because they control the density and distribution of cosmic rays, and they act on the dynamics if the gas. Much of the physics involved in this interplay is encoded in the structure of interstellar magnetic fields. Observations of synchrotron emission and its polarization, asArticle pu...

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Section: Introductionmentioning

confidence: 84%

Planckintermediate results

Aghanim

Alves

Arzoumanian

et al. 2016

A&A

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“…The volume filling factor of these structures decreseases for increasing values of the magnetic Reynolds number R m = R e × P m (Schekochihin et al, 2002;Brandenburg & Subramanian, 2005). The inhomegeneity in the degree of magnetization of matter associated with intermittency is an essential facet of interstellar turbulence (Falgarone et al, 2015;Nixon & Pringle, 2019), which simulations miss because they are far from reproducing the interstellar values of R m . In this context, to make headway, we must follow an empirical approach where a statistical model of interstellar turbulence is inferred from observations.…”

Section: Interstellar Magnetic Fieldsmentioning

confidence: 99%

“…The magnetic structures identified in MHD simulations ( Fig. 6) may be described as filaments, ribbons or sheets with at least one dimension commensurate with dissipation scales of turbulent and magnetic energy in shocks, current sheets or through ambipolar diffusion (Momferratos et al, 2014;Falgarone et al, 2015). While the viscous and Ohmic dissipation scales of turbulence are too small to be resolved by B-BOP, turbulence dissipation due to ion-neutral friction is expected to occur on typical scales between ∼ 0.03 pc and ∼ 0.3 pc (cf.…”

Section: The Promise Of B-bopmentioning

confidence: 99%

“…Left: Projections of the vorticity (the modulus in color) and of the magnetic field (arrows) on the plane of the sky. Right: Small-scale increments of the orientation of the plane of the sky component of the magnetic field, a proxy for the dust polarization angle gradient.Figure adaptedfromFalgarone et al (2015).…”

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confidence: 99%

“…Right: small-scale increments of the orientation of the plane-of-the-sky component of the magnetic field, a proxy for the dust polarisation angle gradient. Source:Figure adaptedfromFalgarone, Momferratos, and Lesaffre (2015).…”

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Probing the cold magnetised Universe with SPICA-POL (B-BOP)

André

Hughes

Guillet

et al. 2019

Publ. Astron. Soc. Aust.

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SPICA, the cryogenic infrared space telescope recently pre-selected for a "Phase A" concept study as one of the three remaining candidates for ESA's fifth medium class (M5) mission, is foreseen to include a far-infrared polarimetric imager (SPICA-POL, now called B-BOP), which would offer a unique opportunity to resolve major issues in our understanding of the nearby, cold magnetized Universe. This paper presents an overview of the main science drivers for B-BOP, including high dynamic range polarimetric imaging of the cold interstellar medium (ISM) in both our Milky Way and nearby galaxies. Thanks to a cooled telescope, B-BOP will deliver wide-field 100-350 µm images of linearly polarized dust emission in Stokes Q and U with a resolution, signal-to-noise ratio, and both intensity and spatial dynamic ranges comparable to those achieved by Herschel images of the cold ISM in total intensity (Stokes I). The B-BOP 200 µm images will also have a factor ∼ 30 higher resolution than Planck polarization data. This will make B-BOP a unique tool for characterizing the statistical properties of the magnetized interstellar medium and probing the role of magnetic fields in the formation and evolution of the interstellar web of dusty molecular filaments giving birth to most stars in our Galaxy. B-BOP will also be a powerful instrument for studying the magnetism of nearby galaxies and testing galactic dynamo models, constraining the physics of dust grain alignment, informing the problem of the interaction of cosmic rays with molecular clouds, tracing magnetic fields in the inner layers of protoplanetary disks, and monitoring accretion bursts in embedded protostars.

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Systematic 2.5D resistive MHD simulations with ambipolar diffusion and Hall effect for fast magnetic reconnection

Landinez,

Lora-Clavijo

2024

Physics Letters A

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The Intermittency of ISM Turbulence: What Do the Observations Tell Us?

Cited by 15 publications

References 54 publications

Planckintermediate results

Planckintermediate results

Probing the cold magnetised Universe with SPICA-POL (B-BOP)

Systematic 2.5D resistive MHD simulations with ambipolar diffusion and Hall effect for fast magnetic reconnection

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