Reexamining the supercritical bound of ion acoustic solitons

Ion acoustic solitons can be generated by a charged object immersed in an electrostatic quasineutral two-temperature plasma flow. These are often described by the forced Korteweg–de Vries equation. Two-fluid simulations of this scenario are conducted and compared to numerical solutions of the forced Korteweg–de Vries equation and theoretical predictions. As in forced Korteweg–de Vries theory, flow regimes are observed where either precursor or pinned solitons are generated depending on the background bulk velocity and object size. However, the critical velocities that govern phase transitions from wakes to precursor and precursor to pinned solitons are found to differ substantially with precursor solitons being much more likely to be produced than previously thought. A theory is derived for the supercritical transition speed which matches the simulation results.