Fully 3D Data-Driven Global MHD Model for Predicting Multiple CME Initiation, Propagation, and Evolution

Growing interest in the adverse effects of space weather has stimulated research on operational models for space weather forecasting. To this end, a new, data-driven, and fully three-dimensional (3D) Sun-to-Earth computational tool is described for predicting both the background solar wind and unsteady propagation of multiple disturbances, including coronal mass ejections (CMEs), based on relevant observational data. The proposed prediction tool encompasses three key components: (i) a semi-empirical model of the solar corona and inner solar wind; (ii) a first-principles global ideal magnetohydrodynamics (MHD) model and numerical method for describing the outer solar wind and propagation of solar disturbances; and (iii) a reduced-order semi-empirical model for representing the initiation of CMEs based on data from available databases. In particular, the current global MHD framework uses a potential field source surface (PFSS) and Schatten current sheet (SCS) model to derive the global coronal magnetic field from photospheric magnetic field observations. The Global Oscillation Network Group (GONG) synoptic maps of the photospheric field are used as input to the potential magnetic field model. Additional empirical Wang-Sheeley-Arge (WSA) type relations are used to associate solar wind plasma properties with the coronal magnetic field and thereby provide inner boundary conditions to the ideal MHD model. A so-called cone model is employed for representing CME initiation based data compiled from online databases, such as the LASCO space weather database. The global MHD model makes use of a finite-volume scheme and either explicit or fully-implicit time-marching schemes to solve the governing ideal MHD partial differential equations on multi-block cubed-sphere meshes. An anisotropic adaptive mesh refinement (AMR) technique provides significant reductions in computational mesh size by locally refining the grid in selected directions as dictated by the solar-wind plasma flow physics. The capabilities of the proposed global MHD framework to predict accurately the background solar wind structure and forecast the solar wind properties at the Earth associated with multiple CMEs are demonstrated for the June 2015 CME event via comparisons with corresponding observations and measurements.