On the Plasma Sheet in Jupiter's Dawn Magnetodisc.

A detailed re-examination was made of the University of Iowa data on energetic electrons during a Pioneer 10 encounter with the plasma sheet in Jupiters dawn magnetodisc at about 51 R sub J Jupiter equatorial radii on 6-7 December 1973. Repeated, also, was the analysis of data on energetic protons for this encounter. On the whole, it appears reasonable to accept the conclusion that very hot plasma characteristic particle energy about 0.1 MeV is an important and probably dominant contributor to the pressure of the plasma confined by the magnetic field in Jupiters dawn magnetodisc. The pressure of energetic protons is greater than that of energetic electrons by a factor of the order of ten. It is plausible that charge neutrality exists for the energetic particles at a number density n of about .003cu.cm. The additional presence of cool plasma is not excluded by present knowledge but an upper limit on its density can be placed on the basis of the relative un-importance of centrifugal pressure.