Probing the structure, composition, and dynamics of the Jovian plasma sheet with energetic particles.

摘要

Jupiter possesses the largest magnetosphere in the solar system through its unique combination of rapid planetary rotation, internal plasma source, and immense intrinsic planetary magnetic field. The nature of its interaction with the solar wind has long been an outstanding question in solar system physics, addressed recently by the unprecedented in situ observations of Jupiter's near-equatorial magnetosphere obtained by the orbiting Galileo spacecraft. The Energetic Particles Detector (EPD) aboard Galileo is particularly well suited to characterize the energy spectra and streaming velocity of the non-thermal Jovian plasma and thereby assess the competing influences of planetary rotation and solar wind momentum transfer on the steady state behavior and temporal variability of the magnetosphere.; This thesis presents a comprehensive characterization of the energetic particle environment in and around the Jovian plasma sheet using measurements of the three-dimensional distribution of protons, oxygen, and sulfur ions with energies between ∼0.01−1 MeV/nucl obtained by the Galileo EPD during its eight year mission from 1995 to 2003. Energetic particle intensities, energy spectral indices, species abundance ratios, and streaming velocities are derived from the EPD measurements and analyzed ratios, and streaming velocities are derived from the EPD measurements and analyzed to characterize their dependence on the orientation of the magnetic field, local time asymmetries arising from the solar wind interaction, and temporal deviations from steady-state structure and dynamics.; The Jovian plasma sheet is detected throughout the duration of the Galileo observations. Significant local time asymmetries are observed in both its local structure and motion as well as its global configuration and dynamics at radial distances as small as 15 R_J. The plasma sheet in the dusk sector is thicker and more disordered relative to that near dawn, where persistent southward non-thermal streaming also is observed. The average streaming velocity itself begins to substantially deviate from rigid corotation with the planet around 25 R_J, consistent with plasma mass loading by the moon Io having a major influence over the plasma convection pattern.