CSAC Stokes Forward Modeling

The interpretation of spectro-polarimetric data is never straightforward, whether because of the caveats of the data themselves (photon noise, polarimetric calibration accuracy or other instrumental effects), or limitations in our knowledge of how to solve the radiative transfer problem (this is the case for certain chromospheric lines, such as H-alpha). For this reason, the interpretation of Stokes profiles has to be approached from several angles. Spectral line inversion techniques can be extremely powerful in some cases, such as for the interpretation of optically thin radiation and of spectral lines formed in the Local Thermodynamical Equilibrium (LTE) regime (photospheric lines). However, there are other situations where forward modeling is the more reasonable approach. In this case, a model of the Sun's atmosphere is used to solve the radiative transfer equation, and the result (a synthetic spectral output) is compared to observations in a qualitative or statistical manner, to assess the validity of the model.

FORWARD is a set of codes intended to be used for forward modeling of various coronal observables, and for accessing and comparing to existing data. Given a coronal model, many different synthetic observables (including Stokes profiles) may be produced, as well as plots of model plasma properties (density, magnetic field, etc.). This community software package was developed by Sarah Gibson (HAO) and collaborators, and is available through SolarSoft. For more information and installation manuals, please go here.

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