Solar atmosphere radiative transfer model comparison based on 3D MHD simulations

Abstract

Context. The reconstruction of the solar spectral irradiance (SSI) on various time scales is essential for the understanding of the Earth’s climate response to the SSI variability. Aims. The driver of the SSI variability is understood to be the intensity contrast of magnetic features present on the Sun with respect to the largely non-magnetic quiet Sun. However, different spectral synthesis codes lead to diverging projections of SSI variability. In this study we compare three different radiative transfer codes and carry out a detailed analysis of their performance. Methods. We perform the spectral synthesis at the continuum wavelength of 665 nm with the Code for Solar Irradiance, and the Rybicki-Hummer, and Max Planck University of Chicago Radiative MHD codes for three 3D MHD simulations snapshots, a non-magnetic case, and MHD simulations with 100 G, and 200 G magnetic field strength. Results. We determine the intensity distributions, the intensity differences and ratios for the spectral synthesis codes. We identify that the largest discrepancies originate in the intergranular lanes where the most field concentration occurs. Conclusions. Overall, the applied radiative transfer codes give consistent intensity distributions. Also, the intensity variation as a function of magnetic field strength for the particular 100 G and 200 G snapshots agree within the 2–3% range.

Preface to Monitoring the Earth Radiation Budget and Its Implication to Climate Simulations: Recent Advances and Discussions

“…On the other hand, semiempirical models use solar images and determine the area covered by solar activity features such as network, plage, and sunspots. In addition, the intensity contrast of the solar activity features is determined from synthetic spectra (Haberreiter et al, 2005(Haberreiter et al, , 2021Yeo et al, 2014). Both approaches lead to different trends from solar minimum to minimum, while the overall solar cycle variation is comparable (Matthes et al, 2017).…”

Preface to Monitoring the Earth Radiation Budget and its Implication to Climate Simulations: Recent Advances and Discussions

“…On the other hand, semi-empirical models use solar images and determine the area covered by solar activity features such as network, plage, and sunspots. In addition, the intensity contrast of the solar activity features is determined from synthetic spectra (Haberreiter et al, 2005(Haberreiter et al, , 2021Yeo et al, 2014). Both approaches lead to different trends from solar minimum to minimum, while the overall solar cycle variation is comparable (Matthes et al, 2017).…”

Solar Hαexcess during Solar Cycle 24 from full-disk filtergrams of the Chromospheric Telescope

“…It is also important from the view of stellar physics to infer the intrinsic emission strengths in individual active regions for different chromospheric lines for stars of varying spectral type and magnetic activity level. Empirical constraints on these quantities will provide guidance for sophisticated 3D magnetohydrodynamic (MHD) radiative transfer models of stellar atmospheres (Freytag et al 2002;Leenaarts & Carlsson 2012;Holzreuter & Solanki 2015;Štěpán et al 2015;Haberreiter et al 2021).…”