Phase angle diffusion of newborn ions in the self-consistently generated fields in solar wind plasmas

The phase angle diffusion, pitch angle diffusion, and energy diffusion of newborn ions in the self-consistently generated fields in solar wind plasmas are studied by means of a one-dimensional electromagnetic hybrid code. For newborn ions, the time for phase angle diffusing to 2π is a little shorter than the time for pitch angle scattering to a relatively thin complete shell, and it is much shorter than the energy scattering time for broadening of the shell toward a thermal distribution. The speed of phase angle diffusion increases monotonously with the injection velocity, but it does not change in the same way with the injection rate. The phase angle diffusion of heavier injected ions is slower than that of lighter injected ions. The complete pickup process of newborn ions should consist of four stages: (1) the creation of the newborn ions and macroperpendicular pickup due to the motional electric field; (2) phase angle diffusion; (3) pitch angle diffusion; and (4) energy diffusion.