Do Hα Stokes V Profiles Probe the Chromospheric Magnetic Field? An Observational Perspective

We investigated the diagnostic potential of the Stokes V profile of the H α line to probe the chromospheric line-of-sight (LOS) magnetic field ( B LOS ) by comparing the B LOS inferred from the weak field approximation (WFA) with that inferred from the multiline inversions of the Ca ii 8542 Å, Si i 8536 Å, and Fe i 8538 Å lines using the STiC inversion code. Simultaneous spectropolarimetric observations of a pore in the Ca ii 8542 Å and H α spectral lines obtained from the SPINOR at the Dunn Solar Telescope on 2008 December 4 are used in this study. The WFA was applied on the Stokes I and V profiles of H α line over three wavelength ranges, viz., around line core (Δ λ = ±0.35 Å), line wings (Δ λ = [−1.5, −0.6], and [+0.6, +1.5] Å), and full spectral range of the line (Δ λ = ± 1.5 Å) to derive the B LOS . We found the maximum B LOS strengths of ∼+800 and ∼+600 G at log τ 500 = −1 and −4.5, respectively, in the pore. The morphological map of the B LOS inferred from the H α line core is similar to the B LOS map at log τ 500 = −4.5 inferred from multiline inversions. The B LOS map inferred from the H α line wings and full spectral range have a similar morphological structure to the B LOS map inferred at log τ 500 = −1. The B LOS estimated from H α using WFA is weaker by a factor of ≈0.53 than that of inferred from the multiline inversions.