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I describe recent progress in terms of 3D hydrodynamical model atmospheres and 3D line formation and their applications to stellar abundance analyses of late-type stars. Such 3D studies remove the free parameters inherent in classical 1D…

天体物理学 · 物理学 2007-05-23 Martin Asplund

Constructing reduced models for turbulent transport is essential for accelerating profile predictions and enabling many-query tasks such as uncertainty quantification, parameter scans, and design optimization. This paper presents…

In this contribution, we present the StaggerGrid, a collaborative project for the construction of a comprehensive grid of time-dependent, three-dimensional (3D), hydrodynamic model atmospheres of solar- and late-type stars with different…

太阳与恒星天体物理 · 物理学 2015-05-30 Remo Collet , Zazralt Magic , Martin Asplund

Theoretical atmosphere models provide the basis for a variety of applications in astronomy. In simplified one-dimensional (1D) atmosphere models, convection is usually treated with the mixing length theory despite its well-known…

太阳与恒星天体物理 · 物理学 2015-06-17 Zazralt Magic , Remo Collet , Martin Asplund

Magnetic geometry has a significant effect on the level of turbulent transport in fusion plasmas. Here, we model and analyze this dependence using multiple machine learning methods and a dataset of > 200,000 nonlinear simulations of…

We investigate the interplay between the ionization radiation from massive stars and the turbulence inside the surrounding molecular gas thanks to 3D numerical simulations. We used the 3D hydrodynamical code HERACLES to model an initial…

太阳与恒星天体物理 · 物理学 2015-06-05 P. Tremblin , E. Audit , V. Minier , W. Schmidt , N. Schneider

The formation of molecular clouds out of HI gas is the first step toward star formation. Its metallicity dependence plays a key role to determine star formation through the cosmic history. Previous theoretical studies with detailed chemical…

In a recent paper the authors presented an extended study aiming at simulating the classical meteorological parameters and the optical turbulence at Dome C during the winter with the atmospherical mesoscale model Meso-NH. A statistical…

天体物理仪器与方法 · 物理学 2010-11-29 Franck Lascaux , Elena Masciadri , Susanna Hagelin

In this paper we show results of numerical simulations for the turbulence in the interstellar medium. These results were obtained using a Riemann solver-free numerical scheme for high-Mach number hyperbolic equations. Here we especially…

星系天体物理 · 物理学 2011-02-11 R. Kissmann , J. Kleimann , H. Fichtner , R. Grauer

The modelling of astrophysical systems such as binary neutron star mergers or the formation of magnetars from the collapse of massive stars involves the numerical evolution of magnetised fluids at extremely large Reynolds numbers. This is a…

高能天体物理现象 · 物理学 2023-10-20 Miquel Miravet-Tenés , Pablo Cerdá-Durán , Martin Obergaulinger , José A. Font

Supersonic turbulence in molecular clouds is a dominant agent that strongly affects the clouds' evolution and star formation activity. Turbulence may be initiated and maintained by a number of processes, acting at a wide range of physical…

星系天体物理 · 物理学 2014-11-20 C. M. Brunt , M. H. Heyer , M. -M. Mac Low

We have computed line emission cooling rates for the main cooling species in models of interstellar molecular clouds. The models are based on numerical simulations of super-sonic magneto-hydrodynamic (MHD) turbulence. Non-LTE radiative…

天体物理学 · 物理学 2009-11-06 M. Juvela , P. Padoan , A Nordlund

We discuss HD and MHD compressible turbulence as a cloud-forming and cloud-structuring mechanism in the ISM. Results from a numerical model of the turbulent ISM at large scales suggest that the phase-like appearance of the medium, the…

天体物理学 · 物理学 2007-05-23 Enrique Vazquez-Semadeni

MHD Turbulence is common in many space physics and astrophysics environments. We first discuss the properties of incompressible MHD turbulence. A well-conductive fluid amplifies initial magnetic fields in a process called small-scale…

星系天体物理 · 物理学 2015-06-19 Andrey Beresnyak , Alex Lazarian

The outer envelopes of massive ($M\gtrsim10\,M_{\odot}$) stars exhibit large increases in opacities from forests of lines and ionization transitions (particularly from iron and helium) that trigger near-surface convection zones.…

太阳与恒星天体物理 · 物理学 2023-07-19 William Schultz , Lars Bildsten , Yan-Fei Jiang

The probability density function (PDF) of the gas density in subsonic and supersonic, isothermal, driven turbulence is analyzed with a systematic set of hydrodynamical grid simulations with resolutions up to 1024^3 cells. We performed a…

太阳与恒星天体物理 · 物理学 2014-11-27 Lukas Konstandin , Philipp Girichidis , Christoph Federrath , Ralf S. Klessen

We performed numerical simulations of supersonic isothermal turbulence driven by mostly compressive large-scale forcing, using both a static grid and adaptive mesh refinement with an effective resolution N=768^3. After a transient phase…

天体物理学 · 物理学 2009-11-13 Wolfram Schmidt , Christoph Federrath , Markus Hupp , Sebastian Kern , Jens C. Niemeyer

Cool giant and supergiant star atmospheres are characterized by complex velocity fields originating from convection and pulsation processes which are not fully understood yet. The velocity fields impact the formation of spectral lines,…

太阳与恒星天体物理 · 物理学 2018-02-21 K. Kravchenko , S. Van Eck , A. Chiavassa , A. Jorissen , B. Freytag , B. Plez

Despite the simplicity of theoretical models of supersonically turbulent, isothermal media, their predictions successfully match the observed gas structure and star formation activity within low-pressure (P/k < 10^5 K cm^-3) molecular…

We analyse extinction maps of nearby Giant Molecular Clouds to forge a link between driving processes of turbulence and modes of star formation. Our investigation focuses on cloud structure in the column density range above the self…

星系天体物理 · 物理学 2015-05-28 J. Rowles , D. Froebrich