POSITION AND SHAPE OF THE VENUS BOW SHOCK - PIONEER VENUS ORBITER OBSERVATIONS

In this study magnetometer data from the Pioneer Venus Orbiter is used to examine the position and shape of this planet's bow shock. Utilizing crossings identified on 86 occasions during the first 65 orbits a mean shock surface is defined for sun‐Venus‐satellite angles of 60‐110°. Both the shock shape and variance in location are found to be very similar to the terrestrial case for the range in SVS angle considered. Howeverwhile the spread in shock positions at the earth is due predominantly to the magnetopause location varying in response to solar wind dynamic pressureionopause altitude variations can have little effect on total obstacle radius. Thusthe Cytherean shock is sometimes observed much closer to or farther from the planet than previously predicted by gasdynamic theory applied to the deflection of flow about a blunt body which acts neither as source nor sink for any portion of the flow. Copyright 1979 by the American Geophysical Union.