On the importance of fluff on the electric behaviour of cosmic grains

A model is created to describe the effects of “fluff” on the potential and electric field on and close to a charged spherical body embedded in a plasma. The consequences are investigated for dust grains biased at positive or negative potentials, but large enough for electron or ion field emission to be active, especially grains in magnetospheric plasmas. Electron emission reduces the floating potential, whereas ion emission destroys the fluff or even the grain itself. Effects of encounters are discussed. The model also characterizes the levitation of small solid particles from larger bodies.