Reconnection at Ganymede: Work in Progress

1. Reconnection at Ganymede:Work in Progress Bill Paterson & Glyn Collinson NASA GSFC

2. 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 Neubauer, 1998

3. Corotation – Jupiter’s plasma rotates with the planet Ganymede orbit

4. CLOCKWORK MOONS (INTELLIGENT DESIGN?) Io Volcanoes Europa Oceans

5. The Perfect Reconnection Machine Flow BG BJ

6. Galileo Near Encounters With Ganymede

7. Magnetic Fields and Dipole Superposition During 4 Encounters

9. G02 Downstream Encounter Jovian Plasma Ganymede Plasma IONS ELECTRONS

10. Paty, Paterson and Winglee, JGR 2008

11. No Cold Ions? No Illumination

12. Ganymede Plasma No Cold Ions? Atmosphere Not Illuminated Jovian Plasma Jovian Plasma IONS ELECTRONS Magnetopause Electrons

13. G08 Ganymede Flyby Measured and Simulated Magnetosphere Jia et al., JGR, 2010

14. NO RESPONSE BELOW ~ 1KEV SENSORS E1, E2, E4, E5, E6, E7 NO RESPONSE AT ALL SENSOR E3 E2, E4, E6 WELL MATCHED SENSITIVITY ABOVE ~ 1 KEV PROVIDE SYMMETRIC COVERAGE

15. Key Questions • What are the origins of the Beams • What is the topology of the Field

29. SO2 plume on Io. Io radius = 1815 km. 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. The Io Plasma Torus inside Jupiter’s magnetosphere

30. NASA is considering two possible future missions to Jupiter. Both are in accord with recent recommendations of the NRC-SSB Decadal Survey. • 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. • 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.

31. 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.