Acceleration of Small Dust Grains due to Charge Fluctuations
  We consider the acceleration of very small dust grains including Polycyclic
Aromatic Hydrocarbons (PAHs) arising from the electrostatic interactions of
dust grains that have charge fluctuations in time due to charging events. We
simulate the charge fluctuations of very small grains due to their sticking
collisions with electrons and ions in plasma, and the emission of
photoelectrons by UV photons using Monte Carlo method. We identify the
acceleration induced by the charge fluctuations as the dominant acceleration
mechanism of very small grains in the diffuse interstellar medium (ISM). We
show that this acceleration mechanism is efficient for environments with low
degree of ionization (i.e., large Debye length), where the charge fluctuations
are slow but have a large amplitude. We also discuss the implications of the
present mechanism for grain coagulation and shattering in the diffuse ISM,
molecular clouds, and protoplanetary disks.
