Surface dielectric barrier discharges (DBDs) have been proposed as actuators for flow control. In this paper we discuss the basic mechanisms responsible for the electrohydrodynamic (EHD) force exerted by the discharge on the gas molecules. A two-dimensional fluid model of the DBD is used to describe the plasma dynamics, to understand the basic physics associated with the EHD force and to give some quantitative estimation of the force under simplified conditions. The results show that for ramp or sinusoidal voltage waveforms, the discharge consists of large amplitude short current pulses during which a filamentary plasma spreads along the surface, separated in time by long duration, low current discharge phases of a Townsend or corona type. The contribution of the low current phases to the total force exerted by the discharge on the gas is dominant because their duration is much longer than that of the current pulses and because the force takes place in a much larger volume. A description of the different discharge regimes and a parametric study of the EHD force as a function of voltage rise time and dielectric thickness is presented.

The NASCAP computer code is used to compute the charging the discharging characteristic p, of a typical communications satellite in geosynchronous orbit. For the case of a severe substorm, satellite surface differential charging in sunlight is found to be sub-stantiallyless than that required to produce discharges in ground simulation studies. A discharge process is postulated involving discharges triggered at edges (or imperfection) followed by discharges to space. The characteristics of such discharges are parametrically varied to evaluate the possible effects on the satellite. it has beenfound that discharge characteristics inferred from satellite monitors could be caused by predicted space discharges, that single cell discharges to space can reduce Surface potential over entire satellite, and that low-density electron trajectory computations indicate that discharge generated electrons may not return to the satellite by long trajectories. Current tran-sients predicted do not agree with the available ground simulation results indicating that additional work must be done both analytically and experimentally to understand and tully explain these discrepancies. 17. P. R. Aron and