The role pickup ions play in the termination shock

The termination shock (TS) is a quasi-perpendicular shock with broad regions on both sides that are populated by high energy ions. These energetic particles play an important role in the formation of the TS structure, which distinguishes it from planetary bow shocks. The pressure of the pickup ions is calculated by solving numerically the Vlasov equation in a time-stationary one-dimensional model shock with the parameters taken from the TS observations. The solution is obtained by backward tracing of the ion trajectories in the shock front. It is found that, in order to maintain the shock stationarity, the upstream density of the pickup ions should be comparable to the density of the solar wind protons.