GUMICS4 Synthetic and Dynamic Simulations of the ECLAT Project

The European Commission funded the European Cluster Assimilation Techniques (ECLAT) project as a collaboration of five leader European universities and research institutes. A main contribution of the Finnish Meteorological Institute (FMI) is to provide a wide range of global MHD runs with the Grand Unified Magnetosphere Ionosphere Coupling simulation (GUMICS). The runs are divided in two categories: synthetic runs investigating the extent of solar wind drivers that can influence magnetospheric dynamics, as well as dynamic runs using measured solar wind data as input. Here we consider the first set of runs with synthetic solar wind input. The solar wind density, velocity and the interplanetary magnetic field had different magnitudes and orientations; furthermore two F10.7 flux values were selected for solar radiation minimum and maximum values. The solar wind parameter values were constant such that a constant stable solution was archived. All configurations were run several times with three different (-15°, 0°, +15°) tilt angles in the GSE X-Z plane. The Cray XT supercomputer of the FMI provides a unique opportunity in global magnetohydrodynamic simulation: running the GUMICS-4 based on one year real solar wind data. Solar wind magnetic field, density, temperature and velocity data based on Advanced Composition Explorer (ACE) and WIND measurements are downloaded from the OMNIWeb open database and a special input file is created for each Cluster orbit. All data gaps are replaced with linear interpolations between the last and first valid data values before and after the data gap. Minimum variance transformation is applied for the Interplanetary Magnetic Field data to clean and avoid the code of divergence. The Cluster orbits are divided into slices allowing parallel computation and each slice has an average tilt angle value. The file timestamps start one hour before the perigee to provide time for building up a magnetosphere in the simulation space. The real measurements were extrapolated into one minute intervals by the database and the time steps of the simulation result are shifted by 20-30 minutes calculated from the spacecraft position and the actual solar wind velocity. All simulation results are saved every 5th minutes (in calculation time). The result of the 162 simulations named so called "synthetic run library" were visualized and uploaded to the homepage of the FMI after validation as well as the year run savings. Here we present details of these runs.