Investigation of recovery of stellar magnetic field geometries from simulated spectropolarimetric data

Sammanfattning: Powerful remote sensing techniques can covert time variability of polarization profiles of stellar spectral lines into vector magnetic fields maps of stellar surfaces. These techniques are widely applied to interpret observations but have been tested using only simplistic tests. It would be of interest to test magnetic inversion methods using polarization spectra simulated for realistic and physical models of stellar magnetic fields provided by recent 3D numerical simulations. Doppler Imaging is a method to reconstruct vector magnetic field maps of stellar surfaces from variation of polarization profiles. The work in this thesis presents numerical experiments to evaluate the performance of Magnetic Doppler Imaging (MDI) code INVERS10. The numerical experiments showed that in given high-resolution observations in four Stokes parameters, the code is capable of reconstructing magnetic field vector distributions, over the stellar surface, simultaneously and without any prior assumptions about the magnetic field geometry. Input data consists of polarization measurements in the line profiles and the reconstruction is performed by solving the regularized inverse problem. Right results were obtained by testing different type of models covering simple, complex and unusual complex magnetic field distribution. Whilst using incomplete Stokes parameter datasets containing only Stokes I and V profiles, the INVERS10 code was able to reconstruct a global stellar magnetic fields of only simple models and give accurate and reliable results. Testing the code with different inclination and azimuth angle successfully gave the lowest deviation when same values are used from the true map.