Milne-Eddington inversion of the Fe I line pair at 630~nm

Abstract

The iron lines at 630.15 and 630.25 nm are often used to determine the physical conditions of the solar photosphere. A common approach is to invert them simultaneously under the Milne-Eddington approximation. The same thermodynamic parameters are employed for the two lines, except for their opacities, which are assumed to have a constant ratio. We aim at investigating the validity of this assumption, since the two lines are not exactly the same. We use magnetohydrodynamic simulations of the quiet Sun to examine the behavior of the ME thermodynamic parameters and their influence on the retrieval of vector magnetic fields and flow velocities. Our analysis shows that the two lines can be coupled and inverted simultaneously using the same thermodynamic parameters and a constant opacity ratio. The inversion of two lines is significantly more accurate than single-line inversions because of the larger number of observables.

Accepted for publication in Astronomy and Astrophysics (Research Note)

References in corpus (4)

• The Solar Optical Telescope for the Hinode Mission: An Overview
• On the validity of the 630 nm Fe I nm lines for the magnetometry of the internetwork quiet Sun
• The usefulness of analytic response functions
• Applicability of Milne-Eddington inversions to high spatial resolution observations of the quiet Sun

Cited by in corpus (7)

• Inferring the magnetic field vector in the quiet Sun. I. Photon noise and Selection Criteria
• Analysis of Quiet-Sun Internetwork Magnetic Fields Based on Linear Polarization Signals
• Comparison of inversion codes for polarized line formation in MHD simulations. I. Milne-Eddington codes
• Applicability of Milne-Eddington inversions to high spatial resolution observations of the quiet Sun
• Chromospheric observations and magnetic configuration of a supergranular structure
• On the effect of oscillatory phenomena on Stokes inversion results
• Neural translation for Stokes inversion and synthesis