EUHFORIA: Heliospheric wind and CME evolution

EUHFORIA provides the heliospheric wind derived from a magnetogram, with superposed CMEs defined by the user or uploaded from a database.

The EUHFORIA (European Heliospheric FORecasting Information Asset) model aims to provide a full Sun-to-Earth modelling chain combining efficient data-driven, semi-empirical, forward approaches with physics-based models wherever appropriate. It consists of two parts, viz. a coronal module and a heliospheric solar wind module that enables superimposed CME evolution. The modules can be run together or each module can be run separately if wanted. The aim of the coronal module is to provide the required MHD input quantities at 21.5 Rs for the heliospheric solar wind module. The coronal module in EUHFORIA is data-driven and combines a PFSS magnetic field extrapolation from GONG or ADAPT magnetograms (1 – 2.5 Rs) with the semi-empirical Wand-Sheely-Arge (WSA) model and the Schatten current sheet (SCS) model to extend the velocity and magnetic field from 2.5 Rs to 21.5 Rs. This is done in combination with other semi-empirical formulas so that also the density and the temperature is given at 21.5 Rs.The heliosphere module of EUHFORIA ( Pomoell and Poedts, 2018) provides the solar wind from 21.5 Rs to 2 AU (or further if necessary). Input at 21.5Rs is provided by a coronal module, for example, EUHFORIA-Corona. It initially extends the (purely radial) velocity and magnetic field to 2 AU and subsequently relaxes this initial MHD solution by applying a rotating inner boundary to create the solar background wind in a relaxed state. This yields a steady solar wind from 21.5 Rs to 2 AU in the co-rotating frame, as the inner boundary condition is not updated, but merely rotated. The coordinate system of the model is HEEQ.Apart from providing the background solar wind, the EUHFORIA-heliosphere model is also able to launch CME models superimposed on the background solar wind. Therefore, it can simulate CME evolution up to 2 AU (and beyond, if required). It currently has the classic cone CME model fully supported and a novel Gibson-Low flux-rope CME model is being under development. In contrast with the classic cone model, the Gibson-Low flux-rope model not only enables to model the CME shock evolution but also the internal magnetic structure of the IP magnetic cloud following the shock. The magnetic field of the CME is not modelled with the cone model. The Gibson-Low model was added into EUHFORIA recently and is not yet capable of predicting the flux rope parameters for efficient forecasting. However, in the future efforts will be made towards this goal and the VSWMC will be a great way to test the prediction capabilities of this flux-rope model.