220 likes | 398 Vues
Voyager Results Revisited. By Ed Sittler NASA/GSFC CAPS Team Meeting #28 Marseille, France July 26-28, 2004. Voyager Encounter Geometry. Saturn Encounter Trajectories. Saturn’s Magnetospheric Plasma. Voyager 1 Plasma Electrons. Voyager 2 Plasma Electrons. Voyager 1 Electron Spectrum.
E N D
Voyager Results Revisited By Ed Sittler NASA/GSFC CAPS Team Meeting #28 Marseille, France July 26-28, 2004
Saturn’s Outer Magnetosphere Energetic Ion and Electron Events
OH Cloud with Saturn’s Inner Magnetosphere (HST Observations)
Enrichment of Nitrogen Ion’s within Saturn’s Inner Magnetosphere? • Solar wind source of keV protons and alphas • Titan Torus as source of keV Nitrogen Ions • Ions energized as they diffuse inward to form radiation belts within inner magnetosphere. • Radial diffusion and Convection • Charged particle sinks • Wave scattering by MHD waves • Satellite sweeping • Loss due to dust particles • Charge exchange losses with neutral clouds
800 keV Electrons Starting at L = 7 Static Solar Wind (V = 400 km/s) Dawn Dusk
Energy Spectrum of Ions and Electrons within Titan’s Neutral Torus
Summary • Voyager plasma data showed presence of light ion component (H+) and heavy ion component (N+,O+,W+). Did not see evidence of H2+. • Data consistent with heavy ions dominating near equator and light ions dominating at high latitudes. • Electron observations show plasma sheet within inner magnetosphere inside L ~ 15 and time dependent region in outer magnetosphere. • Electron data shows keV electrons confined near equatorial plane (T/Tll >> 1). Same is true for energetic electrons (LECP). • Expect energetic heavy ions to be confined to equatorial plane, while protons more isotropic and at all latitudes (LECP). • PLS observed hot keV ion component (N+/O+) confined to equatorial plane in Titan torus region (T/Tll >> 1). Hot keV ion component (N+, O+, W+) also observed at Dione’s L shell ring plane crossing. • Ions typically sub-corotate in outer magnetosphere at ~ 50% of co-rotation. Ionospheric pederson height conductivity ~ 0.2 mho. • Saturn’s magnetosphere falls in the category of a fast rotator where neutral clouds can dominate the plasma environment by number.