Experiments on collisional grain charging of micron-sized preplanetary dust

Collisions between micron-sized grains and larger objects with velocities up to several 10 m s(-1) are believed to be an important physical process in the solar nebula with respect to the preplanetary dust aggregation. Former collision experiments demonstrated that grain-target collisions of micron-sized particles were marked by obvious electrostatic effects. Among those were the observation of particles which, after mechanical rebound, returned to the target and finally stuck, and of particle deposition on targets influenced by the presence of conducting materials. Therefore, it is clear that the dust aggregation process cannot adequately be described without investigating collisional grain charging experimentally. We present experiments on the collisional grain charging of micron-sized grains impacting target surfaces which, in contrast to former work, consist both of nonconducting material and the experiments involving smaller particles than before. Collisional grain charging is stronger than previously discussed with respect to preplanetary grains and should be considered concerning the preplanetary dust aggregation, the formation of lightning in the solar nebula, and a coupling of charged grains to magnetic fields.