Sunward flow in Jupiter's magnetosheath

The position of Voyager crossings of Jupiter's bow shock show a dependence on solar wind pressure to the −1/3 power. This dependence is used to calculate typical bow shock speeds of 50 km/s from Voyager solar wind plasma data. Since the bow shock and magnetopause move approximately in unison in response to solar wind pressure changes, the resulting movement of the magnetosheath at a sizeable fraction of the solar wind speed leads to reversed, sunward flow in large portions of the dayside region when the boundaries are expanding. Voyager 1 plasma data show evidence of such reversed flow.