Improving 3D Reconstruction of the solar corona by regularized tomography with radial weighting

Knowledge of the 3D electron density structure is very important for our understanding of fundamental physical processes in the solar corona, such as coronal heating and acceleration of the solar wind. The 3D density distributions of the full corona can be obtained by solar rotational tomography reconstructions using polarized (pB) or total brightness observations from white-light coronagraphs. They have been used to infer valuable information such as the hydrodynamic structure, heating requirement, and magnetic structure by comparison with that predicted by the global MHD modeling. In this study, we propose to improve the regularized tomography technique by adding a radially dependent weighting factor in the regularization term based on empirical density models or globally averaged pB profile. We use this method to reconstruct the coronal electron density from white-light pB images observed with the SOHO LASCO/C2 and STEREO COR1-A and -B coronagraphs and compare the result with that predicted by thermodynamic MHD simulations and the location of heliospheric current sheet predicted by WSA model. We find that the improved method can significantly improve recovery of the coronal density structures in a wide range of heights by efficiently reducing the smoothing effect on the solution at lower heights and suppressing the occurrence of oscillatory behavior at higher heights.