The energy of waves in the photosphere and lower chromosphere: III. Inversion setup for Ca II H spectra in local thermal equilibrium

摘要

The Ca II H line is one of the strongest lines in the solar spectrum andprovides continuous information on the solar atmosphere from the photosphere tothe lower chromosphere. We describe an inversion approach that reproducesobserved Ca II H spectra assuming LTE. We developed an inversion strategy basedon the SIR code. The approach uses a two-step procedure with an archive ofpre-calculated spectra to fit the line core and a subsequent iterativemodification to improve the fit in the line wing. Simultaneous spectra in the630nm range can optionally be used to fix the continuum temperature. The methodretrieves 1D temperature stratifications neglecting lateral radiativetransport. LOS velocities are included by an empirical approach. An archive ofabout 300.000 pre-calculated spectra is more than sufficient to reproduce theline core of observed Ca II H spectra both in quiet Sun and in active regions.The final thermodynamical stratifications match observed and best-fit spectrato a level of about 0.5 (1) % of Ic in the line wing (core). Inversion schemesbased on pre-calculated spectra allow one a reliable and relatively fastretrieval of solar properties from observed chromospheric spectra. The approachcan be easily extended to an 1D NLTE case by a simple exchange of thepre-calculated archive spectra.