Simultaneous Spectropolarimetric Observations in the Hα and Ca II 8662Å Lines of an Active Region

Abstract

We present spectropolarimetric observations of an active region recorded simultaneously in the Hα and the Ca II 8662 Å lines. The sunspot exhibits multiple structures, including a light bridge and a region where the Ca II 8662 Å line core is in emission. Correspondingly, the Hα line core image displays brightening in the emission region, with the spectral profiles showing elevated line cores. The stratification of the line-of-sight magnetic field is inferred through nonlocal thermodynamic equilibrium multiline inversions of the Ca II 8662 Å line and the weak field approximation (WFA) over the Hα line. The field strength inferred from the Hα line core is consistently smaller than that inferred from inversions at log t500 = −4.5. However, the study finds no correlation between the WFA over the core of the Hα line and that inferred from inversions at log t500 = −4.5. In regions exhibiting emission features, the morphology of the magnetic field at log t500 = −4.5 resembles that at log t500 = −1, with slightly higher or comparable field strengths. The magnetic field morphology inferred from the core of the Hα line is also similar to that inferred from the full spectral range of the Hα line in the emission region. The field strength inferred in the light bridge at log t500 = −1 is smaller than the surrounding umbral regions and comparable at log t500 = −4.5. Similarly, the field strength inferred in the light bridge from the WFA over the Hα line appears lower compared to the surrounding umbral regions.