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Aims: We derive the probability density functions (PDFs) of column density for a complete sample of prominent molecular cloud complexes closer than 200 pc. Methods: We derive near-infrared dust extinction maps for 23 molecular cloud…

Astrophysics of Galaxies · Physics 2015-05-14 J. Kainulainen , H. Beuther , T. Henning , R. Plume

While second and higher order correlations of the light distribution have received extensive study, the lowest order probability distribution function (PDF) -- the probability that a unit volume of space will emit a given amount of light --…

Astrophysics · Physics 2009-11-07 Jeremiah P. Ostriker , Kentaro Nagamine , Renyue Cen , Masataka Fukugita

This letter provides the first prediction of the probability density function (PDF) of flux $R$ in plasma sheath sheath region in magnetic fusion devices which is characterized by dynamical equations with exponential non-linearities. By…

Plasma Physics · Physics 2015-05-13 Johan Anderson , Eun-jin Kim

The vorticity random field of turbulent flow is singled out as the main dynamical variable for the description of turbulence, and the evolution equation of the probability density function (PDF) of the vorticity field has been obtained.…

Fluid Dynamics · Physics 2022-02-23 Jiawei Li , Zhongmin Qian , Mingrui Zhou

The formula for probability density functions (PDFs) has been extended to include PDF for energy dissipation rates in addition to other PDFs such as for velocity fluctuations, velocity derivatives, fluid particle accelerations, energy…

Statistical Mechanics · Physics 2009-11-11 T. Arimitsu , N. Arimitsu

The power spectrum (PS) of the density field in supersonic turbulence is a fundamental quantity that characterizes the statistical properties of the structures formed in compressible flows. It is also widely used to estimate the Mach number…

Astrophysics of Galaxies · Physics 2026-05-12 Pierre Dumond , Jérémy Fensch , Gilles Chabrier , Noé Brucy

Turbulence structure resulting from multi-fluid or multi-species, variable-density isotropic turbulence interaction with a Mach 2 shock is studied using turbulence-resolving shock-capturing simulations and Eulerian (grid) and Lagrangian…

Fluid Dynamics · Physics 2020-01-08 Yifeng Tian , Farhad A. Jaberi , Daniel Livescu

The heating, acceleration, and pitch-angle scattering of charged particles by MHD turbulence are important in a wide range of astrophysical environments, including the solar wind, accreting black holes, and galaxy clusters. We simulate the…

Solar and Stellar Astrophysics · Physics 2013-08-26 Jacob W. Lynn , Ian J. Parrish , Eliot Quataert , Benjamin D. G. Chandran

We present numerical simulations of decaying hydrodynamic turbulence initially driven by solenoidal (divergence-free) and compressive (curl-free) driving. Most previous numerical studies for decaying turbulence assume an isothermal equation…

Astrophysics of Galaxies · Physics 2020-11-25 Jeonghoon Lim , Jungyeon Cho

It has been recently shown that molecular clouds do not exhibit a unique shape for the column density probability distribution function (Npdf). Instead, clouds without star formation seem to possess a lognormal distribution, while clouds…

Volume and column density PDFs in molecular clouds are important diagnostics for understanding their general structure. We developed a novel approach to trace the cloud structure by varying the lower PDF cut-off and exploring a suggested…

Solar and Stellar Astrophysics · Physics 2013-08-02 Orlin Stanchev , Sava Donkov , Todor V. Veltchev , Rahul Shetty

Supersonic turbulence in molecular clouds is a key agent in generating density enhancements that may subsequently go on to form stars. The stronger the turbulence - the higher the Mach number - the more extreme the density fluctuations are…

Astrophysics of Galaxies · Physics 2015-05-18 Chris Brunt

Modeling the structure of molecular clouds depends on good methods to statistically compare simulations with observations in order to constrain the models. Here we characterize a suite of hydrodynamical and magnetohydrodynamical (MHD)…

Astrophysics · Physics 2007-05-23 Mordecai-Mark Mac Low , Volker Ossenkopf

We study local power fluctuations in numerical simulations of stationary, homogeneous, isotropic turbulence in two and three dimensions with Gaussian forcing. Due to the near-Gaussianity of the one-point velocity distribution, the…

Statistical Mechanics · Physics 2009-11-13 M. M. Bandi , Sergei G. Chumakov , Colm Connaughton

The time evolution of the probability density function (PDF) of the mass density is formulated and solved for systems in free-fall using a simple appoximate function for the collapse of a sphere. We demonstrate that a pressure-free collapse…

Astrophysics of Galaxies · Physics 2015-06-17 Philipp Girichidis , Lukas Konstandin , Anthony P. Whitworth , Ralf S. Klessen

We report results of a three dimensional, high resolution (up to 512^3) numerical investigation of supersonic compressible magnetohydrodynamic turbulence. We consider both forced and decaying turbulence. The model parameters are appropriate…

Astrophysics · Physics 2009-10-30 James M. Stone , Eve C. Ostriker , Charles F. Gammie

We derive a multifractal model for the velocity probability density distribution function (PDF), which is valid from the inertial range to the viscous range. The model gives a continuous evolution of velocity PDFs from large to small…

chao-dyn · Physics 2008-02-03 Jens Eggers , Z. Jane Wang

This Letter provides a theoretical interpretation of numerically generated probability density functions (PDFs) of intermittent plasma transport events. Specifically, nonlinear gyrokinetic simulations of ion-temperature-gradient turbulence…

Plasma Physics · Physics 2010-11-10 Johan Anderson , Pavlos Xanthopoulos

Random processes play a crucial role in scientific research, often characterized by distribution functions or probability density functions (PDFs). These PDFs serve as essential approximations of the actual and frequently undisclosed…

Methodology · Statistics 2023-06-06 Nico Schick

We investigate the statistics of turbulence in emulsions of two-immiscible fluids of same density. We compute for the first time velocity increments between points conditioned to be located in the same phase or in different phases and…

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