Knowledge of the electron density distribution in the solar corona put constraints on the magnetic field configurations for coronal modelling, and on initial conditions for solar wind modelling, thus providing valuable information on large-scale structures such as coronal holes, active regions and streamers.
We work with polarised SOHO/LASCO-C2 images from the last two recent minima of solar activity (1996-1997 and 2008-2010), devoid of Coronal Mass Ejections and with heights from 2.5 to 6 R_sun above the solar surface. We derive 3D electron density distributions by applying a newly developed time-dependent tomography reconstruction method to the data. From the empirical 3D distributions, we extract the temporal evolution of the density for polar and equatorial regions, and compare the results between the two solar minima. We discuss their relevance for constructing more realistic models of the solar corona including the density profile with height of Saito and the Potential Field Source Surface model.