In the Jupiter system, the complex plasma torus structures that emerge from the Iogenic plasma source and magnetospheric transport processes are extraordinary, although not well understood. Two of the most interesting and unexplained of these structures, organized near Io's orbit, are (1) the radial distribution of the plasma density clearly observed in both the optical S(+) (6716 Angstroms, 6731 Angstroms) and ultraviolet S(++) (685 Angstroms) emission lines and (2) the System III longitude asymmetry of the ion temperature observed in the S(+) optical emission lines. The so-called plasma ``ribbon,'' the brightest portion of the radial structure, is located just within Io's orbit and has a planetocentric distance that varies with both east-west location about Jupiter and System III longitude. The ion temperature exhibits a minimum in the so-called ``active sector'' located near 200(deg) System III longitude. To study the east-west and System III longitude asymmetries of the ribbon structure, we have developed a time-dependent, two-dimensional plasma transport model (L-shell and System III longitude angle) containing an Io plasma source that moves about Jupiter in the plasma torus described by an offset tilted dipole magnetic field in the presence of an east-west electric field. Preliminary calculations to be presented show that the plasma density evolves in time and produces, as it approaches steady state, a maximum just within Io's orbit. To study the System III asymmetry of the torus, we have undertaken preliminary transport calculations using the Rice Convection Model for Jupiter (RCM-J) and have included a System III longitudinally dependent Pedersen conductivity in the planetary ionosphere. The Pedersen conductivity in the ionosphere near Io's flux tube has a minimum in the active sector because of local maxima of the magnetic field. These RCM-J calculations show that the outward plasma transport rate exhibits a System III longitude dependence. The relationship of this dependence to the asymmetry in the ion temperature will be discussed. Preliminary RCM-J calculations will also be presented to investigate the effects of the subcorotational velocity profile at Io's orbit created by the Iogenic plasma source on the spatial pattern and growth rate of the outward transported plasma ``fingers.''
AAS/Division for Planetary Sciences Meeting Abstracts #28
- Pub Date:
- September 1996