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Filamentary structures are ubiquitous in observations of real molecular clouds, and also in simulations of turbulent, self-gravitating gas. However, making comparisons between observations and simulations is complicated by the difficulty of…

Astrophysics of Galaxies · Physics 2020-10-14 F. D. Priestley , A. P. Whitworth

Understanding the small-scale structure of incompressible turbulence and its implications for the non-local pressure field is one of the fundamental challenges in fluid mechanics. Intense velocity gradient structures tend to cluster on a…

Fluid Dynamics · Physics 2019-04-12 Dimitar G. Vlaykov , Michael Wilczek

Turbulence is essential for understanding the structure and dynamics of molecular clouds and star-forming regions. There is a need for adequate tools to describe and characterize the properties of turbulent flows. One-point probability…

Astrophysics · Physics 2008-11-26 Ralf S. Klessen

Spatial intermittency in decaying kinetic Alfven wave turbulence is investigated to determine if it produces non Gaussian density fluctuations in the interstellar medium. Non Gaussian density fluctuations have been inferred from pulsar…

Astrophysics · Physics 2011-02-11 P. W. Terry , K. W. Smith

The circumgalactic medium (CGM) of nearby star-forming galaxies shows clear indications of OVI absorption accompanied by little to no detectable NV absorption. This unusual spectral signature, accompanied by highly non-uniform absorption…

Astrophysics of Galaxies · Physics 2020-07-01 Edward Buie , William J. Gray , Evan Scannapieco , Mohammadtaher Safarzadeh

This paper reports on 3D numerical simulations of dynamics and thermodynamics in the diffuse ISM. Our models are local, account for sheared galactic rotation, magnetic fields, and realistic cooling, and resolve scales ~1-200 pc. This…

Astrophysics · Physics 2009-11-11 Robert A. Piontek , Eve C. Ostriker

The formation of velocity vortices and density clusters is an intriguing phenomenon of freely cooling granular flows. In this work, the critical length scale $L_c$ for the onset of instability is determined via stability analysis of the…

Statistical Mechanics · Physics 2016-01-20 Vicente Garzó

The main goal of this analysis is to present a new method to estimate the physical properties of diffuse cloud of atomic hydrogen observed at high Galactic latitude. This method, based on a comparison of the observations with fractional…

Astrophysics · Physics 2009-11-13 Marc-Antoine Miville-Deschenes , Peter G. Martin

Numerical and physical experiments on two-dimensional (2d) turbulence show that the differences of transverse components of velocity field are well described by a gaussian statistics and Kolmogorov scaling exponents. In this case the…

Chaotic Dynamics · Physics 2009-10-31 Victor Yakhot

We present a theoretical study of the effects and signatures of realistic velocity field and atmospheric inhomogeneities associated with convective motions at the surface of cool late-type stars on the emergent profiles of iron spectral…

Solar and Stellar Astrophysics · Physics 2014-03-26 Zazralt Magic , Remo Collet , Martin Asplund

Star formation is primarily controlled by the interplay between gravity, turbulence, and magnetic fields. However, the turbulence and magnetic fields in molecular clouds near the Galactic Center may differ substantially from spiral-arm…

Scaling and structural evolutions are contemplated in a new perspective for turbulent channel flows. The total integrated turbulence kinetic energy remains constant when normalized by the friction velocity squared, while the total…

Fluid Dynamics · Physics 2021-05-19 T. -W. Lee

We present an analysis of the internal velocity structures of the newly identified sub-0.1 pc coherent structures, droplets, in L1688 and B18. By fitting 2D linear velocity fields to the observed maps of velocity centroids, we determine the…

We report the evidence for the existence of the universal, continuous turbulent cascade of velocity fluctuations with Kolmogorov -5/3 slope spanning 6 orders of length scales, from $10^4$ pc down to $10^{-2}$ pc. This was achieved by…

Astrophysics of Galaxies · Physics 2022-05-02 Ka Ho Yuen , Ka Wai Ho , Chi Yan Law , Avi Chen , Alex Lazarian

The decay of homogeneous isotropic turbulence in a variable viscosity fluid with a viscosity ratio up to 15 is analyzed by means of highly resolved direct numerical simulations (DNS) at low Reynolds numbers. The question addressed by the…

Fluid Dynamics · Physics 2018-09-21 Michael Gauding , Luminita Danaila , Emilien Varea

FAST HI observations reveal unprecedented internal structures of the high-velocity cloud AC-III, which is found to consist of several coherent subclumps (D1-D6) with nearly constant line widths of $\sim 20~\mathrm{km~s^{-1}}$, while the…

Astrophysics of Galaxies · Physics 2025-10-31 Xunchuan Liu

Supercritical gas filaments in molecular clouds host the dense cores in which new stars form. The mechanisms governing their formation and subsequent gas accretion remain poorly understood. In this study, we conduct a statistical analysis…

(Abridged) We discuss the nonlinear development of the isobaric mode of thermal instability (TI) in the context of the atomic interstellar medium (ISM), in order to assess the ability of TI to establish a well-segregated multi-phase…

Astrophysics · Physics 2009-11-07 F. J. Sanchez-Salcedo , E. Vazquez-Semadeni , A. Gazol

We establish exact inequalities for the structure-function scaling exponents of a passively advected scalar in both the inertial-convective and viscous-convective ranges. These inequalities involve the scaling exponents of the velocity…

chao-dyn · Physics 2009-10-28 Gregory L. Eyink

We study the observable signatures of self-gravitating MHD turbulence by applying the probability density functions (PDFs) and the spatial density power spectrum to synthetic column density maps. We find that there exists three…

Solar and Stellar Astrophysics · Physics 2015-08-06 Blakesley Burkhart , David C. Collins , Alex Lazarian