Plasma fluxes at the intermediate transition of the Venus ionosheath

Abstract

A description of Pioneer Venus Orbiter (PVO) data with evidence of the intermediate transition in the Venus ionosheath is presented. Information on the electric and magnetic field profiles observed across this transition indicates that there are persistent signatures in the behavior of both fields. In many cases the magnetic field intensity decreases to low values in the inner ionosheath and there is a strong rotation of the magnetic field orientation to directions closer to the Sun-Venus line. These variations are also accompanied by a noticeable burst in the 30 kHz electric field noise. Simultaneous changes in the plasma flux have also been identified in association with these variations in the electric and magnetic fields. In some cases the particle flux intensity exhibits a strong increase at the intermediate transition which may be produced by a component of ions of planetary origin. Concepts related to the presence of the intermediate transition are discussed in connection with the structure of supersonic flows streaming past an obstacle. In this later case there is a flow transition located between the shock and the obstacle with properties similar to those observed at the intermediate transition.