CHARGED-PARTICLE PHASE-SPACE DENSITIES IN THE MAGNETOSPHERES OF URANUS AND NEPTUNE

Phase space densities are calculated from measurements of energetic el ectrons and protons made during the Voyager 2 encounters with Uranus a nd Neptune, and they are expressed in terms of the adiabatic invariant s mu, K, and Phi. Low-energy charged particle data are binned by adiab atic invariants using an offset, tilted dipole model of the planetary magnetic field. By this method, no interpolation is necessary in pitch angle or energy, and therefore a much larger fraction of the availabl e data is analyzed here than has been done previously. On the basis of this new binned data set, several outstanding issues of the Uranian a nd Neptunian magnetospheres are addressed, for example, satellite inte raction effects and the variation of spectral properties. Assuming a p ower law spectrum, the spectral index gamma is calculated for data wit hin narrow second-adiabatic-invariant bins. We find the spectral index generally increases with increasing L shell, with local peaks at L sh ells corresponding to maximum absorption locations of planetary satell ites. We also find data indicate that gamma varies strongly with K.