Determine the origin of the discrepant chromospheric magnetic-field measurements

Determine whether the discrepancy between the line-of-sight magnetic fields inferred from the Ca II H and Ca II 854.2 nm lines is caused by differences in noise and magnetic sensitivity, distinct or overlapping height sensitivities, or the weakening and lateral expansion of the magnetic field with height.

Background

The study obtains chromospheric line-of-sight magnetic-field maps using the weak-field approximation for both the Ca II H and Ca II 854.2 nm lines. The Ca II H signal is concentrated mainly above the strongest photospheric field concentrations, whereas Ca II 854.2 nm produces stronger and more spatially extended fields.

The authors explicitly state that the observations alone cannot establish the origin of this discrepancy. They identify several unresolved possibilities, including instrumental and diagnostic noise, differences in the lines’ magnetic sensitivity and formation-height response, and physical weakening or lateral expansion of the magnetic field with height.

References

The origin of this difference cannot be established from the observations alone. It may reflect differences in noise and magnetic sensitivity between the lines, their distinct and overlapping height sensitivities, or the weakening and lateral expansion of the magnetic field with height.

— Chromospheric heating and magnetic topology above the shared penumbra of a delta-spot: Multi-line inversions and multi-height magnetic-field extrapolations  (2608.19983 - Kriginsky et al., 20 Aug 2026) in Section 4.1, “Weak-field approximation results”