  The ion-drag force on a spherical dust particle immersed in a flowing plasma
with external electric field is self-consistently calculated using the Particle
In Cell code SCEPTIC in the entire range of charge-exchange collisionality. Our
results, not based on questionable approximations, extend prior analytic
calculations valid only in a few limiting regimes. Particular attention is
given to the force direction, shown never to be directed opposite to the flow
except in the continuum limit, where other forces are of much stronger
magnitude.
