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1. Title The Magnetosphere of JupiterNew Perspectives from Galileo and Cassini The Magnetosphere of JupiterNew Perspectives from Galileo and Cassini Fran Bagenal University of Colorado Fran Bagenal University of Colorado

2. Comparative Magnetospheres Testing our understanding of Sun-Earth connections through application to other planetary systems

3. Earth~ Dipole Rmp ~ (rV2)-1/6 Compressibility 10 RE solar wind rV2 Jupiter Rmp ~ (rV2)-1/3 100 RJ solar wind rV2

4. Earth ~ Dipole compress 2 Rmp -> 0.7 Rmp 7 RE solar wind rV2 Jupiter Rmp -> 0.5 Rmp 50 RJ solar wind rV2 Factor ~10 variations in solar wind pressure at 5 AU -> observed 100-50 Rj size of dayside magnetosphere

5. b <<1 b ~10 b = nkT B2 /8p

6. Europa Ganymede Io Callisto 1 ton / sec

7. Galileo Mission

8. Galileo Spacecraft spins 3 rpm

9. Voyagers Galileo Orbiter 33 orbits Dec. 1995 to Sep. 2003 Pioneers Solar Wind Cassini flyby Dec. 2000 Magnetopause Ulysses

10. SOLAR WIND Rotation + Outflow EARTH Solar Wind Driven Convection Solar Wind

11. Strong magnetic field 10 hour rotation period Internal plasma source Equatorial plasma disk Corotation with Jupiter Slow outward transport

12. Jupiter - Momentum Coupling Khurana 2001 As plasma from Io flows outwards its rotation decreases (conservation of angular momentum) Sub-corotating plasma pulls back the magnetic field Curl B -> radial current J x B force enforces rotation Field-aligned currents couple magnetosphere to Jupiter’s rotation Cowley & Bunce 2001

13. Disks, B, Stellar Rotation, & Jets John Bally

14. Global Structure & Dynamics • Galileo - Survey of magnetic field in the equator • -> structure and current systems Khurana 2001 Jupiter-like Rotation modifies structure at Jupiter Earth-like

15. Global Structure & Dynamics • Flow Pattern in the Equator • In situ plasma measurements • Rotation dominates to >140 RJ • Local time asymmetry • Observed flow pattern consistent with MHD simulations but ~1.5 times stronger. • Abrupt bursts Bursts Super-rotation EPD data Krupp et al. MHD simulation Ogino et al.

16. Global Dynamics - Outstanding Questions Vasyliunas 1983 • What happens in the magnetotail? • What happens above the equator? • How is angular momentum transferred from Jupiter to the magnetosphere? • What are the roles of Io’s volcanism vs. solar wind in magnetospheric variability? • What triggers disruptions?

17. Satellites in the Magnetosphere Europa & Callisto • Radiolysis of surface • Dynamo in iron core • Magnetosphere within a magnetosphere Galileo NIMS IR image Ganymede • Currents induced by changing field indicate liquid water layer

18. Io 300 km Amirani

19. After quantities of lava are removed from below, the crust cracks and tilts, making tall, blocky mountains. 11 km high Hiiaka Patera Tvashtar 50 km

20. Pilan Plume Io’s Volcanoes& Geysers Prometheus Pilan 5 months apart Pele InfraRed

21. Galileo - Nightside of Io - Visible Glowing Lava Plume Gas & Dust + Aurora

22. After Spencer & Schneider 1996

24. Io-plasma interaction: HST data vs model Jupiter Flow Hubble Space Telescope image of O+ emission- Roessler et al. 1997 MHD model of Io interaction - prediction of O+ emission excited by electron impact- Linker & McGrath 1998

25. Io Plasma Torus UV Source: Extended clouds O, S, SO, SO2, S2..? ~1 ton/s ~3 x 1028 ions/s Dn/n~2% per rotation Warm Torus: 90% of plasma Ne~2000 cm-3 O+ S++ Ti~100eV Te~5eV UV power ~ 2 x 1012 W Cold Torus: Ne~1000 cm-3 S+ Ti~Te~1 eV Local Io Source? ~20%?

26. Io Plasma Torus(Schneider & Trauger) S+

27. Io Plasma Torus • Cassini UVIS - PI Larry Esposito, University of Colorado • Movie - 45 days as Cassini approached Jupiter • Integration over multiple lines in the EUV W brighter E = direction of dipole tilt

28. Image of Torus in O+ Emission S++ Emission Jupiter’s Aurora 110° 200° 290° Wavelength Steffl

29. How do composition, temperatures and UV power vary? Steffl Cassini UVIS 600A 1900A

30. How do composition, temperatures and UV power vary? Steffl 3 1 2 S+++ S++ Tera Watts O+ O+ S+++ S+ Oct Jan Apr 2000 2001

31. Models of Torus Chemistry • Neutral Cloud Theory: • Source = atomic O, S • Ionization, Charge Exchange, Recombination • Radiative Cooling • Ion-Electron coupling - Coulomb collisions • Electron heating: • Necessary to provide UV emitted power • Usually specified as Fhot=Nehot/Necold and Thot • Barbosa, Shemansky, Smith&Strobel, Schreier et al., Lichtenberg, Delamere Atomic data issues

32. Energetic Particle Recycling After Thorne (1983)

33. Energetic Particle Recycling 3 - Energetic Particle Recycling After Thorne (1983)

34. Energetic Particle Recycling • Energetic Neutral Atoms - charge exchange • S+ + O -> O+ + • 50-80 KeV/nucleon • Few % of torus’ 1 ton/sec Cassini MIMI S* • Re-ionization of fast neutral wind • Cassini/MIMI saw pick-up ions • > 2 AU from Jupiter • H+, He++, He+, O+, S+ Molecules?! Krimigis et al.

35. Energetic Particle Recycling Sodium • Extended Fast/Energetic Neutral Wind • Sodium - ground-based telescopic observations of scattered sunlight - cold neutral wind from charge-exchange of torus ions • MIMI observations of hot neutral sulfur and oxygen (molecules?) from charge-exchange of radiation belt particles >2 AU away Mendillo et al. Krimigis et al.

36. Jupiter Radio Emission Discovered in 1955

37. Early Discoveries Io Phase A B B A A B Longitude Io’s Orbital Period = 42 hours Jupiter’s Spin Period = 10 hours Jupiter’s Radio Emission Controlled by - Location of Io - Magnetic Longitude

38. Early Explanations Goldreich & Lyndon-Bell (1969) Dulk (1965)

39. 1979 Voyager flyby - The Io Alfven Wave Looking From Side Io’s motion through Jupiter’s magnetic field induces strong electrical currents which propagate as MHD waves along the field lines towards Jupiter. Looking Upstream

40. Voyager Radio Discoveries Voyager PRA Warwick et al. 1979 • Repeated patterns of arcs in frequency-time spectrographs • Indicates systematic beaming pattern, controlled by the geometry of Jupiter’s magnetic field. Carr et al. 1983

41. Alfven Wave Theory • Io generates Alfven waves • Pattern of reflected waves carried downstream by corotating magnetospheric plasma • Each Alfven wave excites an arc of radio emission. • Nice idea—but probably little wave power reaches high latitudes. Gurnett & Geortz 1982

42. Galileo Io Flyby - 1995 Fresh hot ions Flow Galileo Magnetic field Electron Beams

43. Connerney et al. The Io Aurora Clarke et al. Infrared Io Ultraviolet - energetic particles bombard atmosphere - ‘wake’ emission extends halfway around Jupiter

44. Io Plasma-Atmosphere Interaction • Electrodynamics: Induction and Pick-up currents deflect flow • Heating, ionization and charge-exchange in atmosphere • Cooling, deceleration of upstream plasma • Acceleration of downstream plasma • Messy! Saur et al. 2002 Delamere et al. 2003

45. Phase II: Pick-up of New Plasma in Io’s Wake • Coupling to torus plasma • Alfven travel-time to “edge” of torus • Acceleration to few% of corotation • 2-D MHD in non-uniform background plasma What happens between the torus and Jupiter where the density is very low? Delamere et al. 2003

46. Lessons from FAST at Earth Ergun et al.

47. Ergun et al.

48. EARTH Su et al. 2003 JUPITER 1-D Vlasov code

49. Clarke et al. Aurora Dusk Distortion? Polar storms - Solar Wind Generated? Io wake Main Oval Io footprint

50. Aurora The aurora is the signature of Jupiter’s attempt to spin up its magnetosphere Clarke et al.