Radiation hydrodynamics in simulations of the solar atmosphere

Leenaarts, J.

doi:10.1007/s41116-020-0024-x

Cited by 29 publications

(21 citation statements)

References 77 publications

(126 reference statements)

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“…The discrepancy might be solved by a multi-dimensional approach, but the difficulties connected with multi-dimensional time-dependent non-LTE modeling, namely extremely high computational requirements, do not allow us to represent the observed chromospheric structures directly this way (Carlsson & Leenaarts 2012). A review on radiationhydrodynamic models of the solar atmosphere was recently published by Leenaarts (2020).…”

Section: Introductionmentioning

confidence: 99%

Observational study of chromospheric heating by acoustic waves

Abbasvand

Sobotka

Švanda

et al. 2020

A&A

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Aims. Our aim is to investigate the role of acoustic and magneto-acoustic waves in heating the solar chromosphere. Observations in strong chromospheric lines are analyzed by comparing the deposited acoustic-energy flux with the total integrated radiative losses. Methods. Quiet-Sun and weak-plage regions were observed in the Ca II 854.2 nm and Hα lines with the Fast Imaging Solar Spectrograph (FISS) at the 1.6-m Goode Solar Telescope on 2019 October 3 and in the Hα and Hβ lines with the echelle spectrograph attached to the Vacuum Tower Telescope on 2018 December 11 and 2019 June 6. The deposited acoustic energy flux at frequencies up to 20 mHz was derived from Doppler velocities observed in line centers and wings. Radiative losses were computed by means of a set of scaled non-local thermodynamic equilibrium 1D hydrostatic semi-empirical models obtained by fitting synthetic to observed line profiles. Results. In the middle chromosphere (h = 1000–1400 km), the radiative losses can be fully balanced by the deposited acoustic energy flux in a quiet-Sun region. In the upper chromosphere (h > 1400 km), the deposited acoustic flux is small compared to the radiative losses in quiet as well as in plage regions. The crucial parameter determining the amount of deposited acoustic flux is the gas density at a given height. Conclusions. The acoustic energy flux is efficiently deposited in the middle chromosphere, where the density of gas is sufficiently high. About 90% of the available acoustic energy flux in the quiet-Sun region is deposited in these layers, and thus it is a major contributor to the radiative losses of the middle chromosphere. In the upper chromosphere, the deposited acoustic flux is too low, so that other heating mechanisms have to act to balance the radiative cooling.

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Section: Introductionmentioning

confidence: 99%

Observational study of chromospheric heating by acoustic waves

Abbasvand

Sobotka

Švanda

et al. 2020

A&A

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“…The Lyman-α illumination is often referred to as the Lyman-α incident radiation in the modelling context. Details on the radiative transfer modelling of the photosphere, chromosphere, and corona, are available in, for example, the review by Leenaarts (2020). Prominence modelling was reviewed by, for example, Gibson (2018) and Gunár (2014).…”

Section: Introductionmentioning

confidence: 99%

Quiet-Sun hydrogen Lyman-α line profile derived from SOHO/SUMER solar-disk observations

Gunár

Schwartz

Koza

et al. 2020

A&A

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Context. The solar radiation in the Lyman-α spectral line of hydrogen plays a significant role in the illumination of chromospheric and coronal structures, such as prominences, spicules, chromospheric fibrils, cores of coronal mass ejections, and solar wind. Moreover, it is important for the investigation of the heliosphere, Earth's ionosphere, and the atmospheres of planets, moons, and comets. Aims. We derive a reference quiet-Sun Lyman-α spectral profile that is representative of the Lyman-α radiation from the solar disk during a minimum of solar activity. This profile can serve as an incident radiation boundary condition for the radiative transfer modelling of chromospheric and coronal structures. Because the solar radiation in the Lyman lines is not constant over time but varies significantly with the solar cycle, we provide a method for the adaptation of the incident radiation Lyman line profiles (Lyman-α and higher lines) to a specific date. Moreover, we analyse how the change in the incident radiation influences the synthetic spectra produced by the radiative transfer modelling. Methods. We used SOHO/SUMER Lyman-α raster scans obtained without the use of the attenuator in various quiet-Sun regions on the solar disk. The observations were performed on three consecutive days (June 24, 25, and 26, 2008) during a period of minimum solar activity. The reference Lyman-α profile was obtained as a spatial average over eight available raster scans. To take into account the Lyman-α variation with the solar cycle, we used the LISIRD composite Lyman-α index. To estimate the influence of the change in the incident radiation in the Lyman lines on the results of radiative transfer models, we used a 2D prominence fine structure model. Results. We present the reference quiet-Sun Lyman-α profile and a table of coefficients describing the variation of the Lyman lines with the solar cycle throughout the lifetime of SOHO. The analysis of the influence of the change in the incident radiation shows that the synthetic spectra are strongly affected by the modification of the incident radiation boundary condition. The most pronounced impact is on the central and integrated intensities of the Lyman lines. There, the change in the synthetic spectra can often have the same amplitude as the change in the incident radiation itself. The impact on the specific intensities in the peaks of reversed Lyman-line profiles is smaller but still significant. The hydrogen Hα line can also be considerably affected, despite the fact that the Hα radiation from the solar disk does not vary with the solar cycle.

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“…Driven by the tremendous increases in computational resources over the past decades, computational astrophysics has become an important and rapidly growing discipline of astronomy, including solar physics. Radiation hydrodynamic simulations [1] of the solar atmosphere have come a long way since the pioneering work by Nordlund [2]. While even today’s most sophisticated models are numerical experiments that should not be trusted as accurate renderings of the Sun, recent three-dimensional radiation hydrodynamic simulations have given fascinating new insights into numerous physical phenomena occurring in the Sun’s atmosphere, e.g.…”

Section: Introductionmentioning

confidence: 99%

Acoustic-gravity wave propagation characteristics in three-dimensional radiation hydrodynamic simulations of the solar atmosphere

Fleck¹,

Carlsson

Khomenko

et al. 2020

Phil. Trans. R. Soc. A.

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There has been tremendous progress in the degree of realism of three-dimensional radiation magneto-hydrodynamic simulations of the solar atmosphere in the past decades. Four of the most frequently used numerical codes are Bifrost, CO5BOLD, MANCHA3D and MURaM. Here we test and compare the wave propagation characteristics in model runs from these four codes by measuring the dispersion relation of acoustic-gravity waves at various heights. We find considerable differences between the various models. The height dependence of wave power, in particular of high-frequency waves, varies by up to two orders of magnitude between the models, and the phase difference spectra of several models show unexpected features, including ±180° phase jumps. This article is part of the Theo Murphy meeting issue ‘High-resolution wave dynamics in the lower solar atmosphere’.

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Radiation hydrodynamics in simulations of the solar atmosphere

Cited by 29 publications

References 77 publications

Observational study of chromospheric heating by acoustic waves

Observational study of chromospheric heating by acoustic waves

Quiet-Sun hydrogen Lyman-α line profile derived from SOHO/SUMER solar-disk observations

Acoustic-gravity wave propagation characteristics in three-dimensional radiation hydrodynamic simulations of the solar atmosphere

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