Voyager Results Revisited
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Transcript of Voyager Results Revisited
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
Voyager 2 Electron Spectrum
Voyager Ion Measurements
Voyager 1 Ions at Ring Plane
Saturn’s Radiation Belts
Saturn’s Ring Current
Saturn’s Outer Magnetosphere
Saturn’s Outer Magnetosphere Energetic Ion and Electron Events
OH Cloud with Saturn’s Inner Magnetosphere (HST Observations)
Titan’s Nitrogen Torus
Mimas
Enceladus
Tethys
Dione
Rhea
Neutral N Cloud
Saturn
Particle Density(per cm3)
Titan
(Sputtered from Titan atmosphere at U/(E+U)2)
(Source Rate: 4.5 x 1025 /s)
Radius (Saturn Radii)
Height(Saturn
Radii)
0 5 10 15 20 25 30-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
2.52.32.12.01.81.61.51.31.21.00.80.70.50.30.20.0
Frame 001 22 Mar 2004 Converted Excel DataFrame 001 22 Mar 2004 Converted Excel Data
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
Satellite Sweeping by Rhea
Energy Spectrum of Ions and Electrons at Dione’s L Shell
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.