On the tomography reconstruction of coronal force-free magnetic field

Magnetic field is the main driving force of most plasma phenomena occurring in the inner corona. To understand the physics of the corona, a detailed knowledge of the coronal magnetic field is therefore absolutely essential. But until now, no direct measurement of the magnetic field vector distribution in the corona could be made. Models of the coronal magnetic field rely almost enterely on extrapolationsof photospheric magnetic field observations. Recent progress in spectropolarimetric observations of the coronal emission from magneticaly sensitive coronal ions (Lin et al. 2004) gives a hope that the longitudinal Zeeman effect and Hanle effect could be used to get information about ěc{B} in the corona. However, these observations are LOS integrations through the corona because the respective coronal lines are optically thin. The measurements are therefore not localized and their interpretation is not straightforward. The vector tomography regularized inversion technique could resolve this uncertainity. However, depending on the effect used in the inversion some field configuration cannot be reconstructed. To improve the condition of the inversion problem we enforce a reconstructed field to be a force-free.