Nonlinear wake potential in a dusty plasma

The linear response of a dust grain to a flowing plasma has been well studi ed, both through analytic theory as well as by plasma simulation. The princ ipal feature of the plasma response is a quasi-periodic wavetrain downstrea m of the grain, whose characteristics have been investigated as a function of the plasma conditions and grain properties. In linear theory, the magnit ude of the wake potential scales as the grain charge Q, For large enough ch arge, one expects that nonlinear behavior will occur. Using one- and two-di mensional simulations with particle ions flowing past a fixed charged grain , we show that for sufficiently large Q, the wake potential becomes essenti ally independent of the grain charge, The potential is large enough to refl ect some of the incident ions, which become trapped in the vicinity of the grain, Compared to our previous calculations, we also assume a larger value for the ion-neutral collision frequency, and show that the resulting wake is significantly shorter in length and steadier in time.