# Nicole

NICOLE is a general-purpose synthesis and inversion code for the Stokes profiles emergent from solar/stellar atmospheres. Solar instrumentation is becoming more sophisticated every day and the data sets which are cur- rently available (as well as those expected for the near future) demand the use of modern diagnostic tools in order to retrieve as much information as possible from the observations. The algorithm is described in Socas-Navarro et al (2012, in preparation; see also Socas-Navarro, Trujillo Bueno and Ruiz Cobo 2000). It seeks for the model atmosphere that provides the best fit to the profiles (in a least-squares sense) of an arbitrary number of simultaneously-observed spectral lines.

The underlying hypotheses are:

- Atomic level populations in statistical equilibrium (NLTE), assuming complete angle and frequency redistribution.
- No sub-pixel atmospheric structure is considered, except for a filling factor and a prescribed external atmosphere.
- The observed Stokes profiles are induced by the Zeeman effect in transitions where L-S coupling is a valid approximation (with the exception of the infrared FeI line at 1565.28nm, which has an ad-hoc treatment).
- The hydrostatic equilibrium equation is used to calculate the gas den- sity and the height scale in the atmosphere. This is optional in syn- thesis mode (in that case, the gas pressure/density would be read from the input model) and mandatory in inversion mode
- Undocumented feature for hyperfine structure calculations (please, check with the author for information)

The inversion core used for the development of NICOLE is the LORIEN engine (the Lovely Reusable Inversion ENgine), which combines the SVD technique with the Levenberg-Marquardt minimization method to solve the inverse problem (see Press et al. 1990). I would like to hear comments about people using NICOLE, where you are, what your research is about and what your overall experience with the code is. Please, drop me a line at hsocas@iac.es. If you have complains, criticism or generally speaking have negative things to say, please include the word “cialis” in your message subject ;)

### Download

The code is freely available to the community and can be downloaded here.