EUHFORIA: European heliospheric forecasting information asset

Abstract

The implementation and first results of the new space weather forecasting-targeted inner heliosphere model “European heliospheric forecasting information asset” (EUHFORIA) are presented. EUHFORIA consists of two major components: a coronal model and a heliosphere model including coronal mass ejections. The coronal model provides data-driven solar wind plasma parameters at 0.1 AU by constructing a magnetic field model of the coronal large-scale magnetic field and employing empirical relations to determine the plasma state such as the solar wind speed and mass density. These are then used as boundary conditions to drive a three-dimensional time-dependent magnetohydrodynamics model of the inner heliosphere up to 2 AU. CMEs are injected into the ambient solar wind modeled using the cone model, with their parameters obtained from fits to imaging observations. In addition to detailing the modeling methodology, an initial validation run is presented. The results feature a highly dynamic heliosphere that the model is able to capture in good agreement with in situ observations. Finally, future horizons for the model are outlined.

Effect of the Initial Shape of Coronal Mass Ejections on 3‐D MHD Simulations and Geoeffectiveness Predictions

“…The semi‐empirical coronal model used in this work takes as input synoptic maps of the photospheric magnetic field and computes the solar wind plasma parameters at 0.1 AU by constructing a magnetic field model of the coronal large‐scale magnetic field and employing empirical relations to determine the plasma state at the heliospheric inner boundary. The solar wind speed v sw = v ( f , d ) is determined completely by the properties of the global 3‐D coronal magnetic field, namely, the flux tube expansion factor f and the distance of the foot point of the flux tube to the nearest coronal hole boundary d , as described in Pomoell and Poedts (). The solar wind plasma and magnetic parameters computed by the coronal model are then used as boundary conditions to drive a 3‐D time‐dependent MHD model of the inner heliosphere.…”

“…While a detailed description of the model is given by Pomoell and Poedts (), in this work we discuss the definition of CME shapes in EUHFORIA, focusing in particular on the notion of spherical shape and its implementation in the model. Throughout this work we use a cone model where the CME is described as a hydrodynamic, uniformly filled cloud (i.e., density, pressure, and speed are constant within the CME) characterized by a spherical shape.…”

“…In the cone model implemented in EUHFORIA, the radius of the CME, r 1/2 , is evaluated once the CME starts crossing the heliospheric inner boundary, and it is kept fixed afterward. It is defined by the equation (Pomoell & Poedts, ) where ω is the CME angular width and R is the distance of the heliospheric inner boundary, namely 21.5 R s = 0.1 AU. An illustration is provided in the left panel of Figure .…”

“…Among physics‐based models, ENLIL (Odstrcil et al, ) is the only one that is currently operational and used by space weather forecasting centers in official bulletins (Parsons et al, ). Recent advances in the field have been carried out with the development of the EUHFORIA (EUropean Heliospheric FORecasting Information Asset) heliospheric model (Pomoell & Poedts, ). Both models employ a cone CME model similar to that of Odstrcil et al (), treating the CME as a hydrodynamic cloud characterized by a self‐similarly expanding geometry as the CME evolves in the upper corona, that is, having a constant angular width, propagation direction, and speed (St. Cyr et al, ; Xie et al, ).…”

“…In this work we use the EUHFORIA model described by Pomoell and Poedts () to test the effect of different CME shapes on simulation outputs, in particular on the dynamics of CMEs in the inner heliosphere. This paper discusses the implementation of CME shapes in the model, in particular investigating the notion of “spherical” CME shape and the various alternative implementation approaches that are possible.…”