CMEs are the main driver of Space Weather and very violent events which have been not completely understood. One challenge lies on the difficulty of studying their 3D structure because of the projection effect. By means of the polarization ratio technique we infer the position of the plasma along the line of sight. METIS, the coronograph on board Solar Orbiter, will observe CME in polarized light and will study the 3D structure of CMEs. Our aim is to evaluate the errors associated with the technique.
First we apply the technique to an analytic distribution of plasma and second to the distribution of plasma resulting from a 3D MHD simulation of a flux rope ejection. Using the 3D plasma distribution in the MHD simulation, we synthesize the polarized and total brightness observations of METIS. We apply the polarization technique to the synthesized observations we can estimate the accuracy and the errors of the technique. We provide an interpretation of the results of the technique as the centre of mass of the plasma distribution along a line of sight, we evaluate the error in the position of the centre of mass and direction of propagation of the CME and finally we evaluate the error in the column density measurements obtained from the polarization ratio technique.
In conclusion, our study provides a framework to explore the potential of the METIS Coronograph and to interpret the future polarized light observations of CME in a Space Weather context.