We describe a series of experiments on dust particles flows in a positive
column of a horizontal dc discharge operating in laboratory and microgravity
conditions. The main observation is that the particle flow velocities in
laboratory experiments are systematically higher than in microgravity
experiments, for otherwise identical discharge conditions. The paper provides
an explanation for this interesting and unexpected observation. The explanation
is based on a physical model, which properly takes into account main
plasma-particle interaction mechanisms relevant to the described experimental
study. Comparison of experimentally measured particle velocities and those
calculated using the proposed model demonstrates reasonable agreement, both in
laboratory and microgravity conditions, in the entire range of discharge
parameters investigated.Comment: 9 pages, 7 figure
