Pluto’s plasma wake oriented away from the ecliptic plane

Abstract

Conditions similar to those observed in the solar wind interaction with Venus and Mars where there is a planetary atmosphere in the absence of a global intrinsic magnetic field may also be applicable to Pluto. With up to 24μbars inferred for the Pluto atmosphere it is possible that the feeble solar photon radiation flux that reaches by its orbit, equivalent to ∼10−3 that at Earth, is sufficient to produce an ionization component that can be eroded by the solar wind. In view of the reduced solar wind density (∼10−3 with respect to that at 1AU) that should be available by Pluto its total kinetic energy will be significantly smaller than that at Earth. However, the parameter values that are implied for the interaction process between the solar wind and the local upper ionosphere are sufficient to produce a plasma wake that should extend downstream from Pluto. In view of its low gravity force the plasma wake should have a wider cross-section than that in the Venus and Mars plasma environment. Since Pluto rotates with the axis tilted ∼30° away from the ecliptic plane the plasma wake will be influenced by a Magnus force that has a large component is the north–south solar polar direction. That force will be responsible for propelling the plasma wake with a component that can be directed away from that plane. It is estimated that transport of solar wind momentum to the upper Pluto’s ionosphere implies rotation periods smaller than that of the solid body, and thus large values of the Magnus force that can increase the orientation of the plasma wake away from the ecliptic plane.