Momentum transfer to fluffy dust aggregates from stellar winds

Aims. Dust-plasma interaction may play a dominant role in the dynamics of dust particles around young main-sequence stars. Circumstellar dust is expected to be an aggregate consisting of small grains. The momentum transfer cross section (MTCS) for an aggregate is a key quantity for determining the lifetimes of circumstellar dust disks. Methods. We formulate the MTCS of fluffy dust aggregates and propose an algorithm for computing the MTCS. We compare the magnitude of the plasma and photon Poynting-Roberson effects (PR effects). Results. We find an empirical formula that approximates numerical results well for the MTCSs. A comparison of the magnitudes of the PR effects shows that the lifetime of debris dust around young main-sequence stars is shorter by orders of magnitude than the lifetime estimated by considering the photon PR effect alone. Brief discussion is given on the plasma PR effect for dust debris disks around young main-sequence stars.