reconnection at ganymede: work in progress
DESCRIPTION
Reconnection at Ganymede: Work in Progress. Bill Paterson & Glyn Collinson NASA GSFC. Ganymede Most complex of the plasma interactions because of its magnetic moment. Ganymede has both an oxygen atmosphere [Hall et al., 1998], and a hydrogen exosphere [Barth et al., 1997]. - PowerPoint PPT PresentationTRANSCRIPT
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Reconnection at Ganymede:Work in Progress
Bill Paterson & Glyn CollinsonNASA GSFC
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Neubauer, 1998
Ganymede
Most complex of the plasma interactions because of its magnetic moment.
Ganymede has both an oxygen atmosphere [Hall et al., 1998], and a hydrogen exosphere [Barth et al., 1997].
The equatorial region of the atmosphere is shielded from the external plasma sheet. Thus, atmosphere and ionosphere may be quite different in equatorial and polar regions.
Ganymede exhibits auroral emissions which are not longitudinally symmetric [Feldman et al., 2000].
Galileo - Hot electrons are found near the magnetopause, especially on the upstream side of the interaction. Complex streams of cold ions are found in the downstream region.
Feldman et al., 2000
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Ganymede orbit
Corotation – Jupiter’s plasma rotates with the planet
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CLOCKWORK MOONS (INTELLIGENT DESIGN?)
Io Volcanoes
Europa Oceans
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Flow
BG
BJ
The Perfect Reconnection Machine
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Galileo Near Encounters With Ganymede
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Magnetic Fields and Dipole Superposition During 4 Encounters
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Jovian Plasma Ganymede Plasma
IONS
ELECTRONS
G02 Downstream Encounter
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Paty, Paterson and Winglee, JGR 2008
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No Cold Ions?
No Illumination
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Jovian Plasma
Ganymede PlasmaNo Cold Ions?
Atmosphere Not Illuminated
IONS
ELECTRONS
Jovian Plasma
Magnetopause Electrons
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G08 Ganymede Flyby
Measured and Simulated MagnetosphereJia et al., JGR, 2010
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NO RESPONSE BELOW ~ 1KEV
SENSORS E1, E2, E4, E5, E6, E7
NO RESPONSE AT ALLSENSOR E3
E2, E4, E6
WELL MATCHED SENSITIVITY ABOVE ~ 1 KEV
PROVIDE SYMMETRIC COVERAGE
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Key QuestionsWhat are the origins of the BeamsWhat is the topology of the Field
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Io – Heart of the Jovian Magnetosphere
A chunk of iron, covered with silicates, laced with volatiles.
5.9 RJ from Jupiter.
Stressed by tidal forces, Io spews SO2.
Ionization feeds the magnetosphere at a rate ~1 ton/s.
The plasma is entrained by Jupiter’s magnetic field and rotates with the planet.
It diffuses outward and fills the magnetosphere.
It sweeps past the moons, overtaking them from behind due to rotation of planet and magnetic field.
SO2 plume on Io. Io radius = 1815 km.
The Io Plasma Torus inside Jupiter’s magnetosphere
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NASA is considering two possible future missions to Jupiter. Both are in accord with recent recommendations of the NRC-SSB Decadal Survey.
1) The Jupiter Polar Orbiter, a New Frontiers mission, would placed in a close orbit to determine high-order moments of the gravity field and of the magnetic field, and to observe plasmas near the auroral region and make remote observations of the atmosphere.
2) The Jupiter Icy Moons Orbiter, a flagship-class mission, would visit Callisto, Ganymede, and Europa with multiple goals, but foremost to search for evidence of oceans beneath the ice that might foster life.
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Jupiter itself is inhospitable.
The moons have but thin atmospheres, and are immersed in an extreme radiation environment.
There is little hope for life in this system, unless it is hiding deep beneath the surface of a moon.
Europa is the primary candidate. Surface fissures suggest a layer of something soft or liquid beneath a crust of hard ice.
Magnetic field measurements from Galileo provide an important piece of evidence that seems to corroborate the liquid water scenario.
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