CME propagation in the dynamically coupled space weather tool: COCONUT + EUHFORIA

Context. Numerical MHD models like the European Heliospheric Forecasting Information Asset (EUHFORIA) have been developed\nto predict the arrival time of Coronal Mass Ejections (CMEs) and accelerated high-energy particles. However, in EUHFORIA, transient\nmagnetic structures are injected at 0.1 AU into a background solar wind created from a static solar wind model. This means the\ninserted CME model is completely independent of the coronal magnetic field, missing all potential interactions between the CME and\nthe solar wind in the corona.\nAims. This paper aims to present the time-dependent coupling between the coronal model COolfluid COroNal UnsTructured (COCONUT)\nand the heliospheric forecasting tool EUHFORIA.The first attempt of coupling these two simulations should allow us\nto follow directly the propagation of flux rope from the Sun to Earth.\nMethods. We perform six COCONUT simulations where a flux rope is implemented at the solar surface using either the Titov-\nDémoulin CME model or the Regularized Biot-Savart Laws (RBSL) CME model. At regular intervals, the magnetic field, velocity,\ntemperature, and density of the 2D surface Rb = 21:5 R are saved in boundary files. This series of coupling files is read in a modified\nversion of EUHFORIA to update progressively its inner boundary. After presenting the early stage of the propagation in COCONUT,\nwe examine how the disturbance of the solar corona created by the propagation of flux ropes is transmitted into EUHFORIA. In\nparticular, we consider the thermodynamic and magnetic profiles at L1 and compare them with those obtained at the interface between\nthe two models.\nResults. We demonstrate that the properties of the heliospheric solar wind in EUHFORIA are consistent with those in COCONUT,\nacting as a direct extension of the coronal domain. Moreover, the disturbances initially created from the propagation of flux ropes in\nCOCONUT continue evolving from the corona in the heliosphere to Earth with a smooth transition at the interface between the two\nsimulations. Looking at the profile of magnetic field components at Earth and di erent distances from the Sun, we also find that the\ntransient magnetic structures have a self-similar expansion in COCONUT and EUHFORIA. However, the amplitude of the profiles\ndepends on the flux rope model used and its properties, thus emphasizing the important role of the initial properties in solar source\nregions for accurately predicting the impact of CMEs.\nConclusions. The dynamically coupled COCONUT + EUHFORIA model chain constitutes a new space weather forecasting tool that\ncan predict flux-rope CMEs characteristics upon their arrival at L1.