Jovian plasmaspheres

Plasmaspheres within the Jovian magnetosphere can arise from three distinct types of processes: (1) by a photoelectron (positive ion) flux from the planetary ionosphere (the source type of earth's plasmasphere), (2) by ionization of the atmospheres and neutral particle tori of the satellites, and (3) by ionization of the neutral interstellar medium within the magnetosphere. Loss processes include (1) field‐aligned flux into the planetary atmosphere, (2) recombination, and (3) radial transport. Source strengths are estimated, and the various loss processes are considered to obtain a set of model density profiles for the three types of plasmaspheres. We find that if the photoelectron flux from the planetary atmosphere is strongly trapped, the associated plasmasphere should dominate in number density. However, if the photoelectron flux is in diffusive equilibrium with the atmosphere, the Io‐derived plasmasphere should dominate in number density. In either case the Io‐derived plasmasphere should dominate in mass density because of the heavy ions. The heavy ion plasmasphere can be expected to have important dynamical effects on the magnetosphere in the region beyond about 30 R J . The interstellar plasmasphere can reach densities approaching 10 2 cm −3 when Jupiter is in the high‐interstellar‐density portion of its orbit.