Simulation domain and magnetic topology. Top left: 3D volume of the domain of the simulation with the root blocks of the grid. Bottom left: A 2D cross section at constant angle of ϕ = 0° of the velocity colour at t = 5500 s. This snapshot highlights the spatial distribution of the velocity. The grid block boundaries are delineated by grey lines. Each block contains 8 × 8 × 8 cells. Right: Initial magnetic topological structure. The isosurface of plasma β = 20 (red spheroid) indicates the location of the 3D magnetic null point. Magnetic field lines of distinct connectivity bounding the separatrix surface are represented, either closed (white field lines) or open to the heliosphere (blue field lines).