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

¹ Physikalisch-Meteorologisches Observatorium Davos and World Radiation Center, Dorfstrasse 33, 7260 Davos Dorf, Switzerland
e-mail: margit.haberreiter@pmodwrc.ch
² National Solar Observatory, 3665 Discovery Dr., Boulder, CO 80303, USA
³ High Altitude Observatory, NCAR, PO Box 3000, Boulder, CO 80307, USA
⁴ Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
⁵ Rosseland Centre for Solar Physics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway

Received: 22 August 2020
Accepted: 26 May 2021

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.