Title: Brownian motion of grains and negative friction in dusty plasmas
Authors: S.A.Trigger (Joint Institute for High Temperatures, Russian Academy of Sciences, 13/19 Izhorskaya Str., Moscow 127412, Russia; Humboldt University, 110 Invalidenstr., D-10115 Berlin, Germany), A.G.Zagorodny (Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, 14B Metrolohichna Str., Kiev 03143, Ukraine)

Within the approximation of dominant charging collisions the explicit microscopic calculations of the Fokker-Planck kinetic coefficients for highly-charged grains moving in plasma are performed. It is shown that due to ion absorption by grain the friction coefficient can be negative and thus the appropriate threshold value of the grain charge is found. The stationary solutions of the Fokker-Planck equation with the velocity dependent kinetic coefficient are obtained and a considerable deviation of such solutions from the Maxwellian distribution is established.

Key words: dusty plasma, negative friction, effective temperature, Fokker-Planck equation
PACS: 52.27.Lw, 52.20.Hv, 52.25.Fi