JOVIAN SYSTEM DATA ANALYSIS PROGRAM PROPOSAL SUMMARY

The quantity of magnetic flux crossing the "surface" of Jupiter and entering the jovian magnetosphere is controlled by the strength of the internal dynamo. The mass content of these magnetic flux tubes is controlled by the vigor of the mass loading process at Io that adds ions to the magnetosphere at a rate approaching a ton/second plus some presently unknown contribution from Jupiter's ionosphere. The magnetic flux exiting Jupiter's surface is constant on the time scales relevant to the Galileo mission but the mass content of the flux tubes passing near Io are not because Io is continuously adding ionized mass to the magnetosphere. In steady state there must be a mechanism to remove the ions added from these magnetic field lines. Loss along the field lines into the atmosphere is not sufficiently rapid. If loss along the field line is too slow, then the mass will increase until transport across field lines is sufficient. In an ideal, uniform collisionless plasma the mass is frozen to the magnetic field and the outward transport of ions carries the magnetic flux with it. Particle and field pressure gradient forces and centrifugal forces push the plasma outward against the curvature force of the magnetic field pushing inward. These forces would remain in equilibrium and oppose any motion if the ionosphere were also a perfectly electrically conducting medium, but it is not and the feet of magnetic flux tubes slip. This sets up a circulation pattern in which heavy flux tubes move outward and light, buoyant, flux tubes move inward. To complete the circulation pattern and to remove the build up of heavy ions in the magnetosphere, there must be a mechanism that violates the frozen-in flux theorem to separate the magnetic flux from the particles. This process is reconnection. At Jupiter it pinches off stretched-out field lines producing a magnetic island of dense plasma that exits the magnetosphere down the tail. The shortened flux tube connected to Jupiter moves back to lower radial distances because it is now buoyant. Much of this circulation pattern itself was revealed by the Voyager data but the Galileo mission provides insight into how the processes controlling this circulation occur, and that these processes are transient. Galileo provides constraints on the outflow of material, and on the in flowing magnetic flux tubes. Galileo reveals the time scales involved in magnetospheric reconfigurations and shows the mechanisms responsible for these changes. We have established this sequence of behavior in a series of four articles using single passes examining the dipolar region from 10-25 RJ [Russell et al., 1998a]; across the transition to the magnetodisk [Russell et al., 1998b]; through the magnetodisk region [Russell et al., 1998c], and in the near tail [Russell et al., 1998d] using only the magnetic field measurements. The proposed effort is to extend the study to the entire magnetic prime mission database and to involve ancillary data sets where appropriate to determine where, how often and through what mechanisms the magnetosphere undergoes transient reconfiguration. This task addresses one of the principal magnetospheric objectives of the Galileo mission. It shows how a rapidly rotating magnetized plasma behaves and it illustrates the affect of angular momentum conservation on macroscale plasma processes, a result important to Astrophysics and the Sun-Earth-Connection as well as to Solar System Exploration. The E/PO component of this proposal contributes material to the Michigan Windows to the Universe Website in the area of the jovian magnetosphere. It adds new material, strengthens old material, and creates a three-tiered informational base for the beginning, intermediate and advanced user.