Core-Edge Coupling of Gyrokinetic Code GEM and Fluid Code BOUT++

GEM is a particle-in-cell gyrokinetic turbulence code for the core region of Tokamak. When applied to the tokamak pedestal, GEM is limited by its Dirichlet boundary condition. The pedestal turbulence is strongly coupled to the scrape-off layer turbulence. Setting the turbulence fluctuations at the separatrix to zero, as is typically done in GEM, prevents any spreading of turbulence from the SOL to the pedestal, or vice versa. We are developing an integrated simulation across the core/edge boundary by coupling GEM to BOUT++, which is a fluid turbulence code aiming at the edge. Coupling of the two codes also improves the BOUT++ boundary condition in its inner radial boundary. Firstly, we develop data mapping between GEM and BOUT++. Both codes adopt the field-line-following coordinates. We have developed the mapping based on linear interpolation. Data exchange is based on a memory-based method via ADIOS2. Preliminary results from coupled simulation will be reported.