The best lines to measure temperatures, velocities and magnetic fields in the solar photosphere

An analytical and numerical study of the sensitivity of weak solar photospheric lines to temperatures, velocities, and magnetic fields has been developed. Our investigation is based on the concept of response functions (Ruiz Cobo & del Toro Iniesta 1994). Lines commonly used in solar spectropolarimetry, like Fe I at 630.25 nm in the visible and Fe I 1564.8 nm in the infrared, are examined in detail as emerging from reference quiet Sun and sunspot models. We develop a simple phenomenological model capable of describing the response of any given line to these atmospheric parameters. The relations provided by our model are universal, and can be used to decide which line is best for the particular problem one is dealing with. We find that (a) the sensitivity of the lines to velocities and magnetic fields increases with the sharpness of the intensity and circular polarization profiles, and (b) the sensitivity to temperature is determined mainly by the variation of the source function with temperature, which is smaller at longer wavelengths. The results of this study may be of interest for the design of new instruments and for a better exploitation of existing ones.

 

Fecha: 
09/06/2004 - 14:00
Conferenciante: 
Daniel Cabrera
Filiación: 
Instituto de Astrofísica de Andalucía - CSIC


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