Investigating magnetic field inference from the spectral region around the Mg I <i>b</i>₂ line using the weak-field approximation

Context. The understanding of the magnetic field structure in solar atmosphere is important assessing both dynamics and energy balance atmosphere. Our knowledge about these fields comes predominantly from interpretation spectropolarimetric observations. Simpler approaches based on approximations such as weak-field approximation (WFA) deserve special attention key methods large, high-resolution datasets. Aims. We investigate applicability WFA for retrieving depth-dependent line-of-sight (LOS) spectral region containing Mg I b 2 line two photospheric Ti Fe lines its wings. Methods. constructed applied a 12-level model atom that realistically reproduces profile mean quiet Sun. tested to spectra computed FAL C atmospheric with different velocity added an ad hoc basis . Then we extended analysis 3D magneto-hydrodynamic (MHD) MURaM simulations first MHD cube was used estimate Stokes V formation heights each line. These correspond optical depths at which standard deviation difference between WFA-inferred minimal. estimated were verified using second cube. Results. LOS retrieved by reliable strength up 1.4 kG even when moderate gradients are present. exception line, found strong discrepancy because blend. be: log τ = −2.6, −3.3, −1.8. able uncertainty 150 G only 40 Conclusions. Using WFA, can quickly get observed region. This offers significant advantage comparison otherwise time-consuming classical inversions. find calculated Sun simulation agrees very well spectrum