A5034616681- Astrophysics and Star Formation Studies
- Solar and Space Plasma Dynamics
- Computational Fluid Dynamics and Aerodynamics
- Fluid Dynamics and Turbulent Flows
- Galaxies: Formation, Evolution, Phenomena
- Stellar, planetary, and galactic studies
- Cosmology and Gravitation Theories
- Gas Dynamics and Kinetic Theory
- Astro and Planetary Science
- Atmospheric Ozone and Climate
- Astronomy and Astrophysical Research
- Geophysics and Gravity Measurements
- Advanced Thermodynamics and Statistical Mechanics
- Advanced Combustion Engine Technologies
- Meteorological Phenomena and Simulations
- Scientific Research and Discoveries
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Combustion and flame dynamics
- Material Science and Thermodynamics
- Phase Equilibria and Thermodynamics
- Radio Astronomy Observations and Technology
- Molecular Spectroscopy and Structure
- Ionosphere and magnetosphere dynamics
University of California, San Diego
2013-2023
Lawrence Livermore National Laboratory
2018
University of San Diego
2017
University of California, Santa Barbara
2011
Institut Català de Ciències del Clima
2010
Universitat de Barcelona
2010
Keldysh Institute of Applied Mathematics
2010
Helsinki Institute of Physics
2010
University of Helsinki
2010
Institute of Applied Astronomy
1994-2007
This paper describes the open-source code Enzo, which uses block-structured adaptive mesh refinement to provide high spatial and temporal resolution for modeling astrophysical fluid flows. The is Cartesian, can be run in one, two, three dimensions, supports a wide variety of physics including hydrodynamics, ideal non-ideal magnetohydrodynamics, N-body dynamics (and, more broadly, self-gravity fluids particles), primordial gas chemistry, optically thin radiative cooling metal-enriched plasmas...
We present results of large-scale three-dimensional simulations supersonic Euler turbulence with the piecewise parabolic method and multiple grid resolutions up to 2048^3 points. Our numerical experiments describe non-magnetized driven turbulent flows an isothermal equation state rms Mach number 6. discuss resolution issues demonstrate convergence, in a statistical sense, inertial range dynamics on grids larger than 512^3 The allowed us measure absolute velocity scaling exponents for first...
We use deep adaptive mesh refinement simulations of isothermal self-gravitating supersonic turbulence to study the imprints gravity on mass density distribution in molecular clouds. The show that clouds develops an extended power-law tail at high densities top usual lognormal. associate origin with self-similar collapse solutions and predict power index values range from -7/4 -3/2 agree both observations star-forming
The Padoan and Nordlund model of the stellar initial mass function (IMF) is derived from low order statistics supersonic turbulence, neglecting gravity (e.g. gravitational fragmentation, accretion merging). In this work predictions that are tested using largest numerical experiments hydrodynamic (HD) magneto-hydrodynamic (MHD) turbulence to date (~1000^3 computational zones) three different codes (Enzo, Zeus Stagger Code). predicts a power law distribution for large masses, related energy...
We have implemented an Adaptive Mesh Refinement criterion explicitly designed to increase spatial resolution around discontinuities in the velocity field ENZO cosmological simulations. With this technique, shocks and turbulent eddies developed during hierarchical assembly of galaxy clusters are followed with unprecedented resolution, even at large distances from center. By measuring spectral properties gas field, its time evolution for a reference cluster, we investigate connection between...
We examine the effects of self-gravity and magnetic fields on supersonic turbulence in isothermal molecular clouds with high resolution simulations adaptive mesh refinement. These use large root grids (512^3) to capture four levels refinement density, for an effective 8,196^3. Three Mach 9 are performed, two super-Alfv\'enic one trans-Alfv\'enic. find that gravity splits into populations, low density turbulent state collapsing state. The exhibits properties similar non-self-gravitating this...
Many astrophysical applications involve magnetized turbulent flows with shock waves. Ab initio star formation simulations require a robust representation of supersonic turbulence in molecular clouds on wide range scales imposing stringent demands the quality numerical algorithms. We employ super-Alfvénic decay as benchmark test problem to assess and compare performance nine popular MHD methods actively used model formation. The set codes includes: ENZO, FLASH, KT-MHD, LL-MHD, PLUTO, PPML,...
We study the dynamics of phase transitions in interstellar medium by means three-dimensional hydrodynamic numerical simulations. use a realistic cooling function and generic nonequilibrium initial conditions to follow formation history multiphase detail absence gravity. outline number qualitatively distinct stages this process, including linear isobaric evolution, transition an isochoric regime, filaments voids (also known as "thermal" pancakes), development decay supersonic turbulence,...
We revisit the origin of Larson's scaling laws describing structure and kinematics molecular clouds. Our analysis is based on recent observational measurements data from a suite six simulations interstellar medium, including effects self-gravity, turbulence, magnetic field, multiphase thermodynamics. Simulations isothermal supersonic turbulence reproduce observed slopes in linewidth-size mass-size relations. Whether or not self-gravity included, relation remains same. The relation, instead,...
Enzo (Enzo Developers, 2019a) is a block-structured adaptive mesh refinement code that widely used to simulate astrophysical fluid flows (primarily, but not exclusively, cosmological structure formation, star and turbulence).The community project with dozens of users, has contributed hundreds peer-reviewed publications in astrophysics, physics, computer science.The utilizes Cartesian can be run one, two, or
Probability distribution functions of the total hydrogen column density (N-PDFs) are a valuable tool for distinguishing between various processes (turbulence, gravity, radiative feedback, magnetic fields) governing morphological and dynamical structure interstellar medium. We present N-PDFs 29 Galactic regions obtained from Herschel imaging at high angular resolution (18″), covering diffuse quiescent clouds, those showing low-, intermediate-, high-mass star formation (SF), characterize cloud...
We test a method of estimating the power spectrum turbulence in molecular clouds based on comparison spectra integrated intensity maps and single-velocity-channel maps, suggested by A. Lazarian D. Pogosyan. use synthetic 13CO data from non-LTE radiative transfer calculations density velocity fields simulation supersonic hydrodynamic turbulence. find that yields correct with good accuracy. then apply to Five College Radio Astronomy Observatory map Perseus region, COMPLETE Web site. power-law...
Is the turbulence in cluster-forming regions internally driven by stellar outflows or consequence of a large-scale turbulent cascade? We address this question studying energy spectrum NGC 1333. Using synthetic 13CO maps computed with snapshot supersonic simulation, we show that velocity coordinate method Lazarian & Pogosyan provides an accurate estimate spectrum. then apply to map 1333 from COMPLETE database. find is power law, E(k) ∝ k−β, range scales 0.06 pc ⩽ℓ ⩽ 1.5 pc, slope β = 1.85 ±...
We study the clustering of inertial particles in turbulent flows and discuss its applications to dust protoplanetary disks. Using numerical simulations, we compute radial distribution function (RDF), which measures probability finding particle pairs at given distances, density concentration. The statistics depend on Stokes number, St, defined as ratio friction timescale, τp, Kolmogorov timescale flow. In agreement with previous studies, find that, dissipation range, intensity strongly peaks...
Accretion rates of order 10-8 M☉ yr-1 are observed in young pre-main-sequence (PMS) stars approximately a solar mass with evidence circumstellar disks. The accretion rate is significantly lower for PMS smaller mass, proportional to the second power stellar accr ∝ M2. traditional view that consequence angular momentum transport isolated disks, controlled by disk turbulence or self-gravity. However, these processes not well understood and accretion, fundamental aspect star formation, remains...
Supersonic turbulence plays an important role in a number of extreme astrophysical and terrestrial environments, yet its understanding remains rudimentary. We use data from three-dimensional simulation supersonic isothermal to reconstruct exact fourth-order relation derived analytically the Navier-Stokes equations (Galtier Banerjee, Phys. Rev. Lett., vol. 107, 2011, p. 134501). Our analysis supports Kolmogorov-like inertial energy cascade previously discussed on phenomenological level. show...
We show that simulations of magnetohydrodynamic turbulence in the multiphase interstellar medium yield an E/B ratio for polarized emission from Galactic dust broad agreement with recent Planck measurements. In addition, B-mode spectra display a scale dependence is consistent observations over range scales resolved simulations. The present opportunity to understand physical origin and starting point more refined models use both current future cosmic microwave background experiments.
We performed a series of three-dimensional numerical simulations supersonic homogeneous Euler turbulence with adaptive mesh refinement (AMR) and effective grid resolution up to 1024^3 zones. Our experiments describe non-magnetized driven turbulent flows an isothermal equation state. Mesh on shocks shear is implemented cover dynamically important structures the highest subgrids calibrated match statistics obtained from equivalent uniform simulations. found that at level slightly below 512^3,...
We explore the structure and statistics of multiphase, magnetized ISM turbulence in local Milky Way by means driven periodic box numerical MHD simulations. Using higher order-accurate piecewise-parabolic method on a stencil (PPML), we carry out small parameter survey varying mean magnetic field strength density while fixing rms velocity to observed values. quantify numerous characteristics transient steady-state turbulence, including its thermodynamics phase structure, kinetic energy power...
Three-dimensional, compressible, magnetohydrodynamic turbulence of an isothermal, self-gravitating fluid is analyzed using two-point statistics in the asymptotic limit large Reynolds numbers (both kinetic and magnetic). Following alternative formulation proposed by Banerjee Galtier [Phys. Rev. E 93, 033120 (2016)2470-004510.1103/PhysRevE.93.033120; J. Phys. A: Math. Theor. 50, 015501 (2017)1751-811310.1088/1751-8113/50/1/015501], exact relation has been derived for total energy transfer....
Self-organization is a property of dissipative nonlinear processes that are governed by an internal driver and positive feedback mechanism, which creates regular geometric and/or temporal patterns decreases the entropy, in contrast to random processes. Here we investigate for first time comprehensive number 16 self-organization operate planetary physics, solar stellar galactic cosmology. Self-organizing systems create spontaneous {\sl order out chaos}, during evolution from initially...