ALBERT

Description: The recent global MHD simulation code (REPPU code by Tanaka [2015]) successfully reproduces even observed phenomena such as the auroral breakup of the substorm. We judge that the simulation code correctly reproduces the physical processes of the magnetosphere and ionosphere from the fact that the phenomenon is reproduced realistically. REPPU code employs several empirical parameters expressing the non-MHD mechanisms. We tried to determine the optimal values of the parameters by using the data assimilation technique. For this purpose, we improve the REPPU code to include both the effect of the inclined rotation axis of the Earth and the effect of the discrepancy between the rotational axis and the magnetic axis. Next, we apply the data assimilation technique to determine the ionospheric conductivity distribution which is given as empirical parameters in the original REPPU code. For this purpose, we use the ionospheric electric potential determined by SuperDARN and AE indices. We employed the ensemble variational method as the assimilation technique to obtain the optimal values of the parameters. As a result, we obtained that the ionospheric conductivities are enhanced compared with the empirical results. At the same time, modification of the ionospheric conductivity does not change significantly the magnetosphere. The simulation data become the “reanalysis data” of the space weather which is useful for space weather research. Our future goal is to provide a database of the reanalysis data for space weather.