Fluid dynamic constraints of the Venus ionospheric flow

Abstract

A critical analysis of the current interpretations of the antisolar motion of the Venus ionosphere is presented. It is argued that the pressure gradient forces present across the terminator are not sufficient to produce the observed acceleration of the plasma. A balance condition between the height‐integrated momentum flux of the ionospheric flow and the height‐integrated deficiency of momentum flux of the shocked solar wind in the vicinity of the terminator is formulated in terms of measurable quantities. It is found that the observed 2 to 4‐km/s flow velocities of the upper ionosphere can be readily inferred from such a relation. This result is consistent with the concept that an efficient transport of momentum takes place across the ionopause, and that the bulk of the kinetic energy required to accelerate the Venus ionosphere is derived from the shocked solar wind.