Sound Radiation from Moving Point‐Like Charged Particles in Plasmas

The electrostatic potential and plasma density variations around a point-like charged object in a plasma flow are studied. These objects can represent small charged dust particles, for instance. The radiation patterns can be interpreted as the result of sound waves being radiated by the obstacle. For large electron to ion temperature ratios we find that radiation patterns develop for the sub- as well as the supersonic case. The results are illustrated by numerical simulations using a hybrid Particle In Cell (PIC) code, where the electrons are treated as all isothermal massless fluid, giving a nonlinear Poisson equation. The analytical results are in good agreement with the numerical simulations.