Observation-based Sun-to-Earth simulations of geo-effective Coronal Mass Ejections with EUHFORIA

Coronal Mass Ejections (CMEs) and their Interplanetary counterparts (ICMEs) are the primary source of space weather disturbances at Earth. The key ICME parameters responsible for driving geomagnetic storms are the dynamic pressure and the magnetic field Bz component at Earth, for which reliable predictions are not possible by means of traditional, over-simplified cone CME models. In order to overcome such limitations, the newly developed EUHFORIA heliospheric model has been recently integrated with a magnetised flux rope CME model that allows to model the Interplanetary Magnetic Field (IMF) components associated to ICMEs to a higher degree of accuracy.

In this work we present a Sun-to-Earth comprehensive analysis of a selected set of Earth-directed CMEs, with the aim of testing the space weather predictive capabilities of the new flux rope CME model compared to those of a cone CME model. We first discuss the determination of the CME input parameters based on remote-sensing observations. For each event we reconstruct the CME kinematic and geometric parameters by means of multi-spacecraft reconstruction methods based on coronagraphic CME observations. The magnetic field-related parameters of the flux ropes are estimated based on imaging observations of the photospheric and low coronal source region of the eruption. We then simulate the events with EUHFORIA, using both a cone and a flux rope CME model in order to compare the effect of the different CME kinematical and magnetic input parameters on simulation results at L1. We compare simulation outputs with in-situ observations of the ICMEs and we use them as input for the prediction of global geomagnetic activity indices, comparing them with actual data records. We discuss the prediction performances in terms of solar wind parameters at L1, and ICME geo-effectiveness estimated by means of global geomagnetic activity indices associated to the ICME-driven geomagnetic storms.

First results indicate that using observations close to the Sun to initialize flux rope CMEs in EUHFORIA allows not only to predict their arrival times and dynamical pressures at Earth with a good level of accuracy, but also significantly improves the predictions of their magnetic field properties at 1 AU, which translates into more realistic predictions of ICME-driven geomagnetic storm strengths.