Magnus force in the Venus ionosphere

Abstract

The retrograde superrotation motion of the Venus ionosphere is included in a study of the configuration of the ionospheric transterminator flow by using a fluid‐dynamic interpretation of the interaction that takes place between both flow motions. It is argued that the interaction leads to a fluid dynamic force (Magnus force) that produces an overall (∼10°) dawnward directed deflection of the transterminator flow which is comparable to that implied from the PVO observations. The Magnus force results from a pressure difference that is set across the planet by the difference in the speed of the plasma when both the rotation motion and the transterminator flow are in the same sense (dusk side terminator) to that where both motions are opposite to each other (dawn side terminator). The dawnward deflection of the ionospheric plasma in the transterminator flow also deviates the plasma channels (which serve to account for the ionospheric holes) that extend downstream from the magnetic polar regions and is responsible as well for that of the peak of the histogram of the electron density profiles with an upper ionospheric plateau that are seen near the midnight plane. The effects of the Magnus force are also related to the strong difference in the ionopause altitude observed between the dusk and the dawn side terminator (with higher altitudes seen in the dawn side) and to the larger ionospheric transterminator flow speeds measured at high altitudes by the dawn side terminator.