Diagnostic of Spectral Lines in Magnetized Solar Atmosphere: Formation of the Heta Line in Sunspots
Abstract
Formation of the Hβ λ4861.34 line is an important topic related to the diagnosis of the basic configuration of magnetic fields in the solar and stellar chromospheres. Specifically, broadening of the Hβ λ4861.34 line occurs due to the magnetic and micro-electric fields in the solar atmosphere. The formation of Hβ in the model umbral atmosphere is presented based on the assumption of non-local thermodynamic equilibrium. It is found that the model umbral chromosphere is transparent to the Stokes parameters of the Hβ line, which implies that the observed signals of magnetic fields at sunspot umbrae via the Hβ line originate from the deep solar atmosphere, where τc≈-1 (about 300 km in the photospheric layer for our calculations). This is in contrast to the observed Stokes signals from non-sunspot areas, which are thought to primarily form in the solar chromosphere.