Interstellar turbulence spectrum from in situ observations of Voyager 1

Lee, K. H.; Lee, L. C.

doi:10.1038/s41550-018-0650-6

Cited by 37 publications

(21 citation statements)

References 33 publications

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“…The ISM is inherently multi-scale with a wide range of important physical processes, with power on spatial scales spanning as much as twelve orders of magnitude in just the ionized gas (Chepurnov & Lazarian, 2010;Lee & Lee, 2019). One of the key theoretical questions in star formation is whether the large scales or small scales are the controlling steps in sustaining star formation.…”

Section: Multi-phase Structure Of the Gasmentioning

confidence: 99%

Canadian Investigations of the Interstellar Medium

Hill,

Cami,

Fissel

et al. 2019

Preprint

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Section: Multi-phase Structure Of the Gasmentioning

confidence: 99%

Canadian Investigations of the Interstellar Medium

Hill,

Cami,

Fissel

et al. 2019

Preprint

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“…The turbulent nature of the ISM is well established by the extremely high values of Reynolds number (Elmegreen & Scalo 2004;Kowal et al 2007;Burkhart et al 2009a,b;Schneider et al 2011;Seifried & Walch 2015;Kritsuk et al 2017;Mocz et al 2017;Elia et al 2018;Lee & Lee 2019). The need to progress toward a more precise way to measure the properties of the turbulent motions led to fractal approaches.…”

Section: Introductionmentioning

confidence: 99%

Description of turbulent dynamics in the interstellar medium: multifractal-microcanonical analysis

Yahia

Schneider

Bontemps

et al. 2021

A&A

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Observations of the interstellar medium (ISM) show a complex density and velocity structure, which is in part attributed to turbulence. Consequently, the multifractal formalism should be applied to observation maps of the ISM in order to characterize its turbulent and multiplicative cascade properties. However, the multifractal formalism, even in its more advanced and recent canonical versions, requires a large number of realizations of the system, which usually cannot be obtained in astronomy. We present a self-contained introduction to the multifractal formalism in a "microcanonical" version, which allows us, for the first time, to compute precise turbulence characteristic parameters from a single observational map without the need for averages in a grand ensemble of statistical observables (e.g., a temporal sequence of images). We compute the singularity exponents and the singularity spectrum for both observations and magnetohydrodynamic simulations, which include key parameters to describe turbulence in the ISM. For the observations we focus on the 250 µm Herschel map of the Musca filament. Scaling properties are investigated using spatial 2D structure functions, and we apply a two-point log-correlation magnitude analysis over various lines of the spatial observation, which is known to be directly related to the existence of a multiplicative cascade under precise conditions. It reveals a clear signature of a multiplicative cascade in Musca with an inertial range from 0.05-0.65 pc. We show that the proposed microcanonical approach provides singularity spectra that are truly scale invariant, as required to validate any method used to analyze multifractality. The obtained singularity spectrum of Musca, which is sufficiently precise for the first time, is clearly not as symmetric as usually observed in log-normal behavior. We claim that the singularity spectrum of the ISM toward Musca features a more log-Poisson shape. Since log-Poisson behavior is claimed to exist when dissipation is stronger for rare events in turbulent flows, in contrast to more homogeneous (in volume and time) dissipation events, we suggest that this deviation from log-normality could trace enhanced dissipation in rare events at small scales, which may explain, or is at least consistent with, the dominant filamentary structure in Musca. Moreover, we find that subregions in Musca tend to show different multifractal properties: While a few regions can be described by a log-normal model, other regions have singularity spectra better fitted by a log-Poisson model. This strongly suggests that different types of dynamics exist inside the Musca cloud. We note that this deviation from log-normality and these differences between subregions appear only after reducing noise features, using a sparse edge-aware algorithm, which have the tendency to "log-normalize" an observational map. Implications for the star formation process are discussed. Our study establishes fundamental tools that will be applied to other galactic clouds and simulations in forthcom...

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“…The relatively high transverse velocities of most pulsars effectively scan this spatial variation, leading to pulsar dynamic spectra that vary significantly on timescales of minutes to hours. In the early days of pulsar scintillation studies, pulsar dynamic spectra statistics were used to measure the electron density power spectrum in the interstellar medium on ∼AU and smaller scales (see Rickett 1990 for a review), and thus played an important role in the discovery of the "Big Power Law in the Sky" (Armstrong et al 1995) -that the electron density power spectrum follows a single power-law shape across many orders of magnitude in scale (see also Chepurnov & Lazarian 2010;Lee & Lee 2019).…”

Section: Introductionmentioning

confidence: 99%

Morphology of solar system scale plasma lenses in the interstellar medium: a test from pulsar scintillation parabolic arcs

Shi

2021

Preprint

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Scintillation spectra of some pulsars have suggested the existence of AU scale density structures in the ionized interstellar medium, whose astrophysical correspondence is still a mystery. The detailed study of Brisken et al. (2010) suggested two possible morphologies for these structures: a parallel set of filaments or sheets (the 'parallel stripes model'), or a filament broken up into denser knots (the 'threaded beads model'). Here we propose a straightforward test that can distinguish these two morphologies: whether the apex of the main parabolic arc created by the scattered images deviates from the origin of the scintillation spectrum or not. In the 'parallel stripes' model, the scattered images move along the stripes as the relative position of the pulsar moves. As a result, the pulsar is always co-linear with the scattered images, and thus the apex of the main parabolic arc stays at the origin of the scintillation spectrum. In the 'threaded beads' model, the scattered images remain at almost fixed positions relative to the density structures, and thus the pulsar is not co-linear with the scattered images at most times, leading to an offset between the apex and the origin. Looking for this possible offset in a large sample of pulsar scintillation spectra, or monitoring the evolution of parabolic arcs will help pin down the morphology of these tiny density structures and constrain their astrophysical origin.

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Interstellar turbulence spectrum from in situ observations of Voyager 1

Cited by 37 publications

References 33 publications

Canadian Investigations of the Interstellar Medium

Canadian Investigations of the Interstellar Medium

Description of turbulent dynamics in the interstellar medium: multifractal-microcanonical analysis

Morphology of solar system scale plasma lenses in the interstellar medium: a test from pulsar scintillation parabolic arcs

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