HR: 10:50h
AN: P52B-03    [Abstracts]
TI: The Saturnian Ring Current:
The Role of Suprathermal Pressure.
AU: * Sergis, N
EM: nsergis@phys.uoa.gr
AF: Office of Space Research and Technology, Academy of Athens, Soranou Efesiou 4, Papagos, Athens, 115 27, Greece
AU: Krimigis, S M
EM: Tom.Krimigis@jhuapl.edu
AF: Office of Space Research and Technology, Academy of Athens, Soranou Efesiou 4, Papagos, Athens, 115 27, Greece
AU: Krimigis, S M
EM: Tom.Krimigis@jhuapl.edu
AF: Applied Physics Laboratory, Johns Hopkins University, 11100 Johns Hopkins Road, Laurel, MD 20 723, United States
AU: Mitchell, D G
EM: don.mitchell@jhuapl.edu
AF: Applied Physics Laboratory, Johns Hopkins University, 11100 Johns Hopkins Road, Laurel, MD 20 723, United States
AU: Roelof, E C
EM: Edmond.Roelof@jhuapl.edu
AF: Applied Physics Laboratory, Johns Hopkins University, 11100 Johns Hopkins Road, Laurel, MD 20 723, United States
AU: Hamilton, D C
EM: dch@umd.edu
AF: University of Maryland, Department of Physics, John S. Toll Physics Building, College Park, MD 20 742, United States
AU: Krupp, N
EM: krupp@linmpi.mpg.de
AF: Max-Planck-Institut für Sonnensystemforschung, Max-Planck-Str. 2, Katlenburg-Lindau, 37 191, Germany
AB: On July 1, 2007, Cassini completed three full years orbiting Saturn. The Magnetospheric Imaging Instrument (MIMI) onboard the spacecraft, performs comprehensive measurements of the energetic ion population within the magnetosphere of the planet. Observations of energetic ion directional intensities, energy spectra and ion composition are provided by the Charge Energy Mass Spectrometer (CHEMS) over the range 3 to 220 keV/e and by the Low Energy Magnetospheric Measurements System (LEMMS) that measures ions in the range 0.024 to 18 MeV. Using the suprathermal particle pressure (P_part) distribution over the Saturnian magnetosphere, calculated from the (E>3keV) energetic ion fluxes obtained during the three years of Cassini orbits, we address the driving mechanism of the equatorial azimuthal current system in the Saturnian magnetosphere. We report estimates of the equatorial azimuthal ring current intensity (J_phi) resulting from the radial pressure gradient and compare the inertial (centrifugal) stress to suprathermal particle pressures and their relative significance on the ring current formation and dynamics. Preliminary results indicate that the suprathermal pressure (P_part), is systematically larger compared to the ram pressure of the corotational flow (ρ V²), by approximately one order of magnitude (i.e. 5× 10^{- 10}dyne/cm² vs. 6× 10^-11dyne/cm² for r=10R_S), throughout the ring current region. Furthermore, outside r=11R_S the centrifugal stress (ρ Ømega ²r), appears to be substantially smaller compared to the radial gradient of the suprathermal pressure (dP_part/dr), suggesting that the outer part of the azimuthal ring current is driven principally by suprathermal rather than inertial forces.
DE: 2756 Planetary magnetospheres (5443, 5737, 6033)
DE: 6275 Saturn
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting