VENUS IONOSPHERE' AN INTERPRETATION OF MARINER 10 OBSERVATIONS

The dayside ionosphere of Venus observed by Mariner 10 may be understood in terms of a dyhamic interaction with the solar wind which results in a compressed topside above an "F-2 ledge" consisting of O+ and a dynamically unaffected F-1 layer corresponding to a neutral temperature T similar or equal to 380 degrees K and consisting of O-2(+) and CO2+. The top of the upper ledge appears to be an ionopause caused by solar wind scavenging of He+, representing a solar-wind obstacle consistent with the bow shock observations.