Solar Atmosphere Radiative Transfer Model Comparison based on 3D MHD simulations

TL;DR

This study compares three radiative transfer codes used in 3D MHD solar simulations to assess their consistency in spectral synthesis, revealing small differences mainly in magnetic regions and overall agreement within a few percent.

Contribution

It provides a detailed comparison of radiative transfer codes applied to 3D MHD solar simulations, highlighting their agreement and discrepancies in spectral synthesis.

Findings

Codes produce consistent intensity distributions.

Discrepancies mainly in intergranular lanes with magnetic fields.

Intensity variation differences are within 2-3% for magnetic snapshots.

Abstract

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. 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. We perform the spectral synthesis at the continuum wavelength of 665 nm with the Code for Solar Irradiance (COSI), and the Rybicki-Hummer (RH), and Max Planck University of Chicago Radiative MHD (MURaM) codes for three 3D MHD simulations snapshots, a non-magnetic case, and MHD simulations with 100 G, and 200 G magnetic field strength. 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. 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.