The electrohydrodynamic body force produced in an asymmetric surface dielectric barrier discharge is widely utilized in flow control applications. The mechanism of body force production has a key role in the performance of plasma actuators. In this paper, a novel supplementary theory of body force production, named 'nonlinear force', is described as a new interesting component of total body force. This force is distinct from the well-known body force with a Coulomb origin, and also acts through a different mechanism. The theory of nonlinear force shows that it is unidirectional and pushes all particles towards the lower electrode irrespective of the charge sign and variations in electric field polarity.
