Reconstruction of the electron density distribution in the solar corona based on LASCO C2 observations

From total K-corona intensity images provided by the C2 coronagraph. with orange filter (visible range) we tried to reconstruct the large scale electron density in the corona, using a modelisation based on the assumption of an axisymmetric corona, which allows a separation between the angular and radial descriptions. This method has been successfully applied to the eclipse observations of 1991 and 1994 and gave results up to 3.1 R-.. In the case of LASCO C2, the range extends from 2.3 to 6 R-., where the electron scattering brightness gets less and less predominant. Due to the absence of data for the inner corona, the 3-D reconstruction process could only be performed up to a Legendre polynomial order of 2. We were however able to develop an iterative method to compute the electron scattering polarization rate, leading finally to improved electron density models.