Structure of the solar photosphere studied from the radiation hydrodynamics code ANTARES

Abstract

The ANTARES radiation hydrodynamics code is capable of simulating the solar granulation in detail unequaled by direct observation. We introduce a state-of-the-art numerical tool to the solar physics community and demonstrate its applicability to model the solar granulation. The code is based on the weighted essentially non-oscillatory finite volume method and by its implementation of local mesh refinement is also capable of simulating turbulent fluids. While the ANTARES code already provides promising insights into small-scale dynamical processes occurring in the quiet-Sun photosphere, it will soon be capable of modeling the latter in the scope of radiation magnetohydrodynamics. In this first preliminary study we focus on the vertical photospheric stratification by examining a 3-D model photosphere with an evolution time much larger than the dynamical timescales of the solar granulation and of particular large horizontal extent corresponding to on the solar surface to smooth out horizontal spatial inhomogeneities separately for up- and downflows. The highly resolved Cartesian grid thereby covers of the upper convection zone and the adjacent photosphere. Correlation analysis, both local and two-point, provides a suitable means to probe the photospheric structure and thereby to identify several layers of characteristic dynamics: The thermal convection zone is found to reach some ten kilometers above the solar surface, while convectively overshooting gas penetrates even higher into the low photosphere. An wide transition layer separates the convective from the oscillatory layers in the higher photosphere.

Radiation hydrodynamics in simulations of the solar atmosphere

“…Since the pioneering simulations of Nordlund (1982), a plethora of codes that aim to model solar and/or stellar atmospheres in 3D have been developed. The ones that I am aware of are: Stagger (e.g., Stein and Nordlund 1998, but many different versions of this code exist), MURaM (Vögler 2004;Rempel 2017), Bifrost (Gudiksen et al 2011), COBOLD (Freytag et al 2012), Stellarbox (Wray et al 2015), RAMENS (Iijima and Yokoyama 2015;Iijima 2016), MANCHA3D (Khomenko et al 2017(Khomenko et al , 2018, ANTARES (Leitner et al 2017), and RADMHD (Abbett and Fisher 2012). The latter is the only code that does not use the radiation treatment developed by Nordlund (1982), and instead uses a simpler but much faster method.…”

The solar photospheric silicon abundance according to CO5BOLD

“…3D atmospheres account for the time-dependence and multidimensionality of the flow, and a spectral synthesis using these atmospheres reproduces line shapes and asymmetries. Prominent examples include STAGGER (Magic et al 2013), MuRAM (Vögler et al 2005), Bifrost (Gudiksen et al 2011), and Antares (Leitner et al 2017). In this work, we use CO 5 BOLD , a conservative hydrodynamics solver able to model surface convection, waves, shocks and other phenomena in stellar objects (Freytag et al 2012).…”

Spatially resolved spectroscopy across stellar surfaces

“…High-precision determinations of stellar properties require a detailed modeling of stellar surfaces and an understanding of how the emerging spectrum of radiation is formed. The structure of convective motions can be modeled in some detail with 3D and time-dependent hydrodynamics; such model photospheres are now established as the most realistic descriptions of stellar outer layers, at least in solar-type stars (Beeck et al 2013a;Freytag et al 2012;Kupka & Muthsam 2017;Leenaarts 2020;Leitner et al 2017;Magic et al 2013;Nordlund et al 2009;Trampedach et al 2013;Tremblay et al 2013), with a general agreement among different model families (Beeck et al 2012;Pereira et al 2013).…”