Improving CME evolution and arrival predictions with AMR and grid stretching in Icarus

Abstract: Coronal Mass Ejections (CMEs) are one of the main drivers of disturbances in the interplanetary space. Strong CMEs, when directed towards the Earth, cause geo-magnetic storms upon interacting with the magnetic field of the Earthand can cause significant damage to our planet and affect everyday life. As such, efficient space weather prediction tools are necessary to forecast the arrival and impact of CME eruptions. Recently, a new heliospheric model Icarus was developed based on MPI-AMRVAC, which is a 3D ideal MHD model for the solar wind and CME propagation, and it introduces advanced numerical techniques to make the simulations more efficient. A cone model is used to study the evolution of the CME through the background solar wind and its arrival and impact at Earth. Grid stretching and AMR are combined in the simulations by using multiple refinement criteria. We compare simulation results to the EUFHORIA model. As a result, the simulations were sped up by a factor of 17 for the most optimal configuration in Icarus. For the cone CME model, we found that limiting the AMR to the region around the CME-driven shock yields the best results. The results modelled by the simulations with radial grid stretching and AMR level 4 are similar to the results provided by the original EUHFORIA and Icarus simulations with the 'standard' resolution and equidistant grids. The simulations with 5 AMR levels yielded better results than the simulations with an equidistant grid and standard resolution. Solution AMR is flexible and provides the user the freedom to modify and locally increase the grid resolution according to the purpose of the simulation. The advanced techniques implemented in Icarus can be further used to improve the forecasting procedures, since the reduced simulation time is essential to make physics-based forecasts less computationally expensive.