Aachen PK 2003 – wissenschaftliches Programm

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P: Plasmaphysik

P 4: Poster I

P 4.39: Poster

Montag, 17. März 2003, 17:45–19:15, Foyer

Delayed shielding of a test charge by a dusty plasma with dynamical grain charging — •Michael Raadu and Muhammad Shafiq — Royal Inst Technology, Alfvén Laboratory, Div Plasma Physics, SE-100 44 Stockholm, Sweden

Dynamical grain charging in a dusty plasma modifies the dielectric response function. The charging rate is determined by the random particle currents to a grain and its capacitance (size), and is of the order of the product of the ion plasma frequency with the size in Debye lengths. Changes in the charges on the grains lead to a shielding effect that acts in the same way as Debye shielding but is physically distinct. If the number of negative charges residing on grains becomes comparable to that of plasma electrons, the shielding due to grain charge fluctuations is comparable to the electron Debye shielding. For a slowly moving charge the response due to charge fluctuations is an enhanced total shielding, together with a time delay effect. An alternative analysis is performed introducing a delay operator for the grain charge response. This confirms the interpretation of the standard results. Previous results showing an asymptotic inverse power law potential appear to be erroneous.