Extension of the Muram Radiative MHD Code for Coronal Simulations

Rempel, Matthias

doi:10.3847/1538-4357/834/1/10

Cited by 195 publications

(285 citation statements)

References 48 publications

Supporting

Mentioning

266

Contrasting

Order By: Relevance

“…The simulation by Nordlund (1982) is of Type 5. MURaM (Vögler 2004;Rempel 2017), RAMENS (Iijima and Yokoyama 2015; Iijima 2016), and MAN-CHA3D (Khomenko et al 2017(Khomenko et al , 2018 are Type 2 codes. Stellarbox (Wray et al 2015) is Type 6.…”

Section: Computation Of the Heating Rate From The Intensity And Sourcmentioning

confidence: 99%

Radiation hydrodynamics in simulations of the solar atmosphere

Leenaarts

2020

Living Rev Sol Phys

View full text Add to dashboard Cite

Nearly all energy generated by fusion in the solar core is ultimately radiated away into space in the solar atmosphere, while the remaining energy is carried away in the form of neutrinos. The exchange of energy between the solar gas and the radiation field is thus an essential ingredient of atmospheric modeling. The equations describing these interactions are known, but their solution is so computationally expensive that they can only be solved in approximate form in multi-dimensional radiation-MHD modeling. In this review, I discuss the most commonly used approximations for energy exchange between gas and radiation in the photosphere, chromosphere, and corona.

show abstract

Section: Computation Of the Heating Rate From The Intensity And Sourcmentioning

confidence: 99%

Radiation hydrodynamics in simulations of the solar atmosphere

Leenaarts

2020

Living Rev Sol Phys

View full text Add to dashboard Cite

show abstract

“…In this paper, we use a 3D MHD model that self-consistently shows both long fibrils and flare ribbons. It was computed using the radiation-MHD code MURaM (Vögler et al 2005;Rempel 2017). The computational domain spans over an entire active region, and contains a bipolar sunspot pair.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional modeling of chromospheric spectral lines in a simulated active region

Bjørgen

Leenaarts

Rempel

et al. 2019

A&A

View full text Add to dashboard Cite

Context. Because of the complex physics that governs the formation of chromospheric lines, interpretation of solar chromospheric observations is difficult. The origin and characteristics of many chromospheric features are, because of this, unresolved. Aims. We focus here on studying two prominent features: long fibrils and flare ribbons. To model them, we use a 3D MHD simulation of an active region which self-consistently reproduces both of them. Methods. We model the Hα, Mg ii k, Ca ii K, and Ca ii 8542 Å lines using the 3D non-LTE radiative transfer code Multi3D. To obtain non-LTE electron densities, we solve the statistical equilibrium equations for hydrogen simultaneously with the charge conservation equation. We treat the Ca ii K and Mg ii k lines with partially coherent scattering.Results. This simulation reproduces long fibrils that span between the opposite-polarity sunspots and go up to 4 Mm in height. They can be traced in all lines due to density corrugation. Opposite to previous studies, Hα, Mg ii h&k, and Ca ii H&K, are formed at similar height in this model. Although, some of the high fibrils are also visible in the Ca ii 8542 Å line, this line tend to sample loops and shocks lower in the chromosphere. Magnetic field lines are aligned with the Hα fibrils, but the latter holds to a lesser extent for the Ca ii 8542 Å line. The simulation shows structures in the Hα line core that look like flare ribbons. The emission in the ribbons is caused by a dense chromosphere and a transition region at high column mass. The ribbons are visible in all chromospheric lines, but least prominent in Ca ii 8542 Å line. In some pixels, broad asymmetric profiles with a single emission peak are produced, similar to the profiles observed in flare ribbons. They are caused by a deep onset of the chromospheric temperature rise and large velocity gradients. Conclusions. The simulation produces long fibrils similar to what is seen in observations. It also produces structures similar to flare ribbons despite the lack of non-thermal electrons in the simulation. The latter suggests that thermal conduction might be a significant agent in transporting flare energy to the chromosphere in addition to non-thermal electrons.

show abstract

“…We complement the approach of Rempel (2012) that includes parts of the convection zone below the photosphere to drive the magnetic field. While Rempel (2017) uses more advanced physics, our models are driven by actual photospheric observations and hence are able to match observed structures in the corona directly. This work is a continuation of Pencil Code models, like first presented in Bingert et al (2010) that led to a better understanding on why the cross-section of coronal loops appears as roughly constant (Peter and Bingert 2012).…”

Section: Introductionmentioning

confidence: 99%

Driving solar coronal MHD simulations on high-performance computers

Bourdin

2019

Geophysical & Astrophysical Fluid Dynamics

View full text Add to dashboard Cite

The quality of today's research is often tightly limited to the available computing power and scalability of codes to many processors. For example, tackling the problem of heating the solar corona requires a most realistic description of the plasma dynamics and the magnetic field. Numerically solving such a magneto-hydrodynamical (MHD) description of a small active region (AR) on the Sun requires millions of computation hours on current high-performance computing (HPC) hardware. The aim of this work is to describe methods for an efficient parallelization of boundary conditions and data input/output (IO) strategies that allow for a better scaling towards thousands of processors (CPUs). The Pencil Code is tested before and after optimization to compare the performance and scalability of a coronal MHD model above an AR. We present a novel boundary condition for non-vertical magnetic fields in the photosphere, where we approach the realistic pressure increase below the photosphere. With that, magnetic flux bundles become narrower with depth and the flux density increases accordingly. The scalability is improved by more than one order of magnitude through the HPCfriendly boundary conditions and IO strategies. This work describes also the necessary nudging methods to drive the MHD model with observed magnetic fields from the Sun's photosphere. In addition, we present the upper and lower atmospheric boundary conditions (photospheric and towards the outer corona), including swamp layers to diminish perturbations before they reach the boundaries. Altogether, these methods enable more realistic 3D MHD simulations than previous models regarding the coronal heating problem above an AR -simply because of the ability to use a large amount of CPUs efficiently in parallel.

show abstract

Extension of the Muram Radiative MHD Code for Coronal Simulations

Cited by 195 publications

References 48 publications

Radiation hydrodynamics in simulations of the solar atmosphere

Radiation hydrodynamics in simulations of the solar atmosphere

Three-dimensional modeling of chromospheric spectral lines in a simulated active region

Driving solar coronal MHD simulations on high-performance computers

Contact Info

Product

Resources

About