Effective charge of a small absorbing body in highly collisional plasma subject to an external electric field

The total force which is the resultant of the electric, ion, and electron drag forces has been calculated for a small absorbing spherical grain immersed in a highly collisional, weakly ionized plasma subject to a weak external electric field. Linear dielectric response formalism has been used and both ion and electron absorption on the grain have been taken into account. It is shown that the total force is always directed along the direction of the electric force. The "effective" charge of the grain which can be defined as the ratio of the total force to the strength of the electric field is calculated. It is shown that its magnitude is comparable to the magnitude of the actual grain's charge. (C) 2007 American Institute of Physics.