Development of the flow structure in the midplane for the M1 simulation. The computation domain is initialized with a uniform density and the shear flow of the circumstellar disk. The planetary core accretes gas, and a protoplanetary atmosphere forms around the core. In the orbital direction of the planet, horseshoe orbits form, centered on the sign change of the shear flow. Eventually, the simulation reaches thermodynamic equilibrium, where radiative cooling is fully compensated for by atmosphere-disk recycling. In this equilibrium the gas temperature and the gas density become constant in time. The dashed green circle is the Bondi radius calculated from the local temperature. The Bondi radius shrinks with time because the atmospheric gas heats up when it is compressed. After the simulation reaches thermodynamic equilibrium.