The orientation and motion of the predawn current sheet and Jupiter's magnetotail

Abstract

From the observed times when Pioneer 10 and Voyager 1 observe particle flux maxima and minima and when the magnetic field strength is a minimum we derive a geometric description of the current sheet in Jupiter's magnetosphere. It lags the planetary rotation by an angle δ which varies as a function of radial distance as δ=22° + 0.80 (r‐16.3). The maximum latitude of the current sheet is roughly 10° inside of 60 RJ and decreases beyond. Thus there is a hinge point near 60 RJ. The position of the hinge point moves in response to the external solar wind pressure variation. We discuss the variation of δ(r) theoretically and show how it is related to the magnetic field topology and plasma flow. We conclude that the distant field lines do not corotate with Jupiter and that the Alfven speed at 50 RJ is of the order of 1500 km/s. The topology of the current sheet is affected by centrifugal forces, outward mass transport and solar wind‐magnetosphere interaction. We show how these effects can be related to different current systems.