PLASMA IN THE JOVIAN CURRENT SHEET

In a recent study of the Pioneer 10 observational data in the outer magnetospheric current sheet of Jupiter, Walker, Kivelson, and Schardt conclude that high energy (> 60 keV) ions frequently are dominant contributors to the plasma pressure and suggest that low energy (≤ 5 keV) plasma is of much less importance. These results are dependent in a crucial way on their adopted extrapolation of observed energy spectra of protons to energies considerably lower than the low end of the observed range. We reach essentially opposite conclusions on the basis of (a) a more thorough study of a larger body of proton spectral data and (b) a simple magnetohydrodynamic theory of the current sheet using the observed magnetic field structure. Our specific conclusion is that the dominant contribution to the plasma pressure in the radial range 25 to 62 RJ is by thus‐far unobserved protons (ions) having energies of the order of 0.1 ‐ 10 keV. Copyright 1979 by the American Geophysical Union.