GASDYNAMIC SIMULATIONS OF THE SOLAR-WIND INTERACTION WITH VENUS - BOUNDARY-LAYER FORMATION

A 2-D gasdynamic simulation of the mass-loaded solar wind flow around the dayside of Venus is presented. For average ionopause conditions ne ar 300 km, the simulations show that mass loading from the pickup of o xygen ions produces a boundary layer of finite thickness along the ion opause. Within this layer and toward the ionopause, the temperature de creases and the total mass density increases significantly. Furthermor e, there is a shear in the bulk flow velocity across the boundary laye r, such that the tangential flow decreases in speed as the ionopause i s approached and remains low along the ionopause which is consistent w ith Pioneer Venus observations. Numerical simulations are carried out for various mass addition rates and demonstrate that the boundary laye r develops when oxygen ion production exceeds approximately 2 x 10(5) m-3 s-1.