Coronal density

This module is aimed at providing a quasi real-time determination of the 2D distribution of coronal densities on the plane of the sky.

The electron density distribution in the corona is obtained, with the regular cadence of one hour, from LASCO/C2 images, between 2 and 6 solar radii and in coronal sectors 60-degree wide across the equator. The need to provide electron-density maps with the same frequency as the images from the “Sun now” module, requires to calculate the density using total-brightness data, and not the pB measurements, that are performed by LASCO only once per day.

We use a standard technique consisting in the inversion of the integral along the LOS of the total K-corona, which is due to the Thomson scattering of the solar disk radiation off coronal electrons (see van de Hulst 1950; Hayes et al. 2001). The K-corona brightness is derived from the total coronal brightness after subtraction of a model of the F-corona.