1. University of Colorado
From Core to Solar Wind
Studying the Space Environment of Planets
Thanks to:
Margaret Kivelson
David Brain
Steve Bartlett
Fran Bagenal
University of Colorado

2. The Space Environment of Planets
Ganymede, Mercury - what a magnetic field says about a core - magnetosphere within a magnetosphere Mars - surface magnetization - atmospheric loss Europa, Callisto - radiation of surfaces
- induction in conducting shell -> water Io - volcanism, patchy atmosphere
- aurora Comets + Pluto

3. Planetary Dynamos 1 2 Volume of electrically conducting fluid
... which is convecting
... and rotating 2 1
and
All planetary objects probably have enough rotation - the presence (or not) of a global magnetic field tells us about

4. Scales Magnetospheres of the Giant Planets Earth LARGE
Rotating with planet
Jupiter + Saturn:
dipole with small tilt
dynamo in metallic hydrogen
Uranus + Neptune:
multipole, large tilt
dynamo in water/ammonia/methane layer
Earth

5. Mercury & Ganymede Bsurface ~ 1/100 Earth Diameter of Earth
Mercury - Magnetic field detected by Mariner 10 in 1974
Ganymede - Magnetic field detected by Galileo in 1996
Solar
Wind
Bsurface ~ 1/100 Earth
Diameter of Earth

6. Mercury & Ganymede
What drives convection in these small bodies?
“The test of a good theorist is the ability to explain any outcome, even when the data are wrong”
- David Stevenson
Liquid
Fe + S
Core
MESSENGER 201?
JIMO ?
Iron
Core
-Liquid?
Liquid
Iron
Core

7. Ganymede: A Magnetosphere within a Magnetosphere
Torrence Johnson

8. Ganymede’s mini-magnetosphere controls the motion of energetic charged particles
Ambient magnetic field
Closed Ganymede magnetic field lines
Galileo
Open-closed boundary
Magnetic field coupling Ganymede to Jupiter
Kivelson et al. 1996

9. Aurora on Ganymede Trailing Side = Upstream Leading Side = Downstream
HST observations of oxygen emissions
- McGrath
Trailing Side = Upstream
Leading Side = Downstream
Energetic
Particles
Aurora on Ganymede
Khurana & Pappalardo
North Polar Cap
South Polar Cap

10. Mars Global Surveyor Magnetometer - PI: M. Acuna

11. No core dynamo today
Magnetization of surface rocks

13. Magnetization only of old, cratered terrain
-> Dynamo ceased ~3.5 billion years ago

14. Ionosphere

15. Atmospheric Loss Processes
Neutral
Bulk removal
“stripping”
Ion
Ion pickup
Photochemical loss
Sputtering

16. Crustal magnetic sources affect these processes:
shielding atmosphere from SW
field topology
open field lines

17. MGS Measurements - Implications for Mars’ Atmosphere
Ancient dynamo
-> early protection for atmosphere
Strong crustal magnetization
-> affect atmospheric loss after dynamo turn-off

18. Solar Wind Interaction Boundary
Pressure Balance: obstacle
to the solar wind
PSolar Wind =
P (magnetic)crust
+ P (thermal)ionosphere
David Brain

19. Mars’Interaction Boundary Response to the Solar Wind

20. Field Topology
Solar wind and magnetic field impinging on Mars’ complex magnetic field
Close-up of strong anomaly region
David Brain

21. Changing Topology of Mars’ Magnetic Field

22. Over a Strong Magnetic Region

23. Mars Aeronomy Mission Upper atmosphere Ionosphere Magnetic Field
Pick-Up Ions
Solar Wind

24. Galileo Mission

25. The Galilean Satellites

27. The Magnetosphere of Jupiter New Perspectives from Galileo and Cassini
Title Io
Europa
Ganymede
Callisto
Fran Bagenal
University of Colorado
Think of a moon embedded in a plasma which overtakes the moon in the direction of its orbital motion.

28. Europa & Callisto
Radiolysis -
Bombardment of surface ices and minerals by energetic particles from the magnetosphere
changes chemistry
alters grain size
embedded heavy ions
sputtering
“Because of the magnetosphere, the Galilean satellites have all lost the equivalent of a Titan (or Earth) atmosphere over the past billion years”
- Bob Johnson
THEN - the atmosphere is ionized & stripped away by the magnetosphere
Galileo Near InfraRed Mapping Spectrometer image of Europa showing distribution of hydrated sulfur compounds

29. Induced Currents -> Oceans
A moon sees a changing magnetic field as Jupiter’s tilted magnetosphere rotates
Electrical currents induced in a electrically conducting layer produce a magnetic perturbation - observed by Galileo
Observed magnetic field perturbations imply water layers in Callisto and Europa, possibly Ganymede
Depth and thickness of water layer not uniquely determined
Life!

30. Io
300 km
Amirani

31. Io’s Volcanoes & Geysers
Pilan Plume
Prometheus
Pilan 5 months apart
Pele
Infrared glow

32. Io at night - Galileo visible image
Glowing Lava
Plume Gas & Dust + Aurora

33. After Spencer & Schneider 1996

34. Plasma collides with atmosphere on the flanks

35. 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

36. Io Plasma Torus - ground-based telescope
Source of plasma = 1 ton of sulfur and oxygen ions per second
Schneider & Trauger

37. Cassini UltraViolet Imaging Spectrometer
Larry Esposito, University of Colorado
UV images of the toroidal cloud of ions at Io’s orbit,
The S+ , O+ ions are trapped by Jupiter’s magnetic field.
Jupiter is dark at UV wavelengths. E
W brighter
= direction of dipole tilt

38. Early Radio Observations & Explanations
Radio Beam
Marshall & libby
Piddington & Drake - Goldreich & L-B?
Dulk (1965)
Goldreich & Lyndon-Bell (1969)

39. The Io Aurora Infrared Ultraviolet Io Footprint Aurora
IR, UV spot images
Text -> implications
- energy does get to ionosphere
- but not just at Io footprint
Ultraviolet
- energetic particles bombard atmosphere
- ‘wake’ emission extends half way around Jupiter

40. The aurora is the signature of Jupiter’s attempt to spin up its magnetosphere
Main Oval
Io footprint + wake G E
Clarke et al.

41. Jupiter’s Extended Corona
ENAs
S, O, H
Krimigis et al.
30 Rj
Charge exchange of energetic charged particles with neutral clouds around orbits of Io and Europa -> escaping Energetic Neutral Atoms
=> HUGE clouds
Sodium
500 Rj ~ 1/4 A.U.
Sodium
Mendillo et al.

42. SMall EXplorer mission ~$120M
Earth-orbiting UV telescope to observe Io, the torus and Jovian aurora

43. Juno
Jupiter
Polar
Orbiter
~$650M

44. Solar Wind Interaction with a Comet

45. Comet Borelly
ENERGY
Heavy Ions H+
TIME

46. Deep Space 1

47. Pluto & Charon

48. The solar wind interacts with Pluto’s escaping atmosphere like a comet

49. Thank you!
New Horizons 2016