Magnetic field amplification by collisionless shocks in partially ionized plasmas

In this paper, we study the shock structures of collisionless shocks in partially ionized plasmas by means of two-dimensional hybrid simulations, where the shock is a perpendicular shock with shock velocity $v_{sh}\approx 40v_A\approx 1333km{s}^{-1}$ and the upstream ionization fraction is 0.5. We find that large density fluctuations and large magnetic field fluctuations are generated both in the upstream and downstream regions. In addition, we find that the velocity distribution of downstream hydrogen atoms has three components. The observed shock structures suggest that diffusive shock acceleration can operate at perpendicular shocks propagating into partially ionized plasmas in real three-dimensional systems.