Effect of a dipole moment on the wake potential of a dust grain in a flowing plasma

The effect of a dipole moment on the wake potential of a dust grain in a co llisionless plasma with a supersonic ion flow is studied. It is found that both the point charge and the dipole moment can be responsible for the osci llatory potential behind the dust. The dipole moment is dominant in forming the wake potential when the dipole moment p becomes of the order of \Q\lam bda(D), where Q is the dust charge and lambda(D) is the Debye length.