Plasma in the Jovian current sheet

A large body of spectral data for protons with energies greater than 200 keV has been analyzed. It is concluded that the main body of plasma in the Jovian current sheet observed by Pioneer 10 on its outbound pass probably has an energy well below the lowest threshold of the Pioneer 10 detectors. This premise is examined using a semiempirical model of the magnetic field in the magnetodisk and simple magnetohydrodynamic theory. Results indicate that the dominant contribution to the plasma pressure in the region from 25 to 65 Jovian radii is from as yet unobserved protons (ions) with energies of the order of 0.1 to 10 keV.