The Magnetosphere of Jupiter New Perspectives from Galileo and Cassini Fran Bagenal University of Colorado Title The Magnetosphere of Jupiter New Perspectives from Galileo and Cassini Fran Bagenal University of Colorado

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

Compressibility Earth ~ Dipole R mp ~ (  V 2 ) -1/6 Jupiter R mp ~ (  V 2 ) -1/3 solar wind  V 2 10 R E 100 R J

compress 2 Earth ~ Dipole Jupiter solar wind  V 2 R mp -> 0.5 R mp R mp -> 0.7 R mp Factor ~10 variations in solar wind pressure at 5 AU - > observed Rj size of dayside magnetosphere 7 R E 50 R J

 ~10  <<1  = nkT B 2 /8 

Io Ganymede Europa Callisto 1 ton / sec

Galileo Mission

Galileo Spacecraft spins 3 rpm

Cassini flyby Dec Galileo Orbiter 33 orbits Dec to Sep Voyagers Pioneers Ulysses Solar Wind Magnetopause

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

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

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 Jupiter - Momentum Coupling Field-aligned currents couple magnetosphere to Jupiter’s rotation Khurana 2001 Cowley & Bunce 2001

Disks, B, Stellar Rotation, & Jets John Bally

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

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

Global Dynamics - Outstanding Questions 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? Vasyliunas 1983

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

Io Amirani 300 km

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

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

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

After Spencer & Schneider 1996

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

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

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

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

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

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

How do composition, temperatures and UV power vary? Tera Watts S +++ O+O+ O+O+ S ++ S +++ S+S+ Oct Jan Apr Steffl

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 F hot =Ne hot /Ne cold and T hot Barbosa, Shemansky, Smith&Strobel, Schreier et al., Lichtenberg, Delamere Atomic data issues

Energetic Particle Recycling After Thorne (1983)

3 - Energetic Particle RecyclingEnergetic Particle Recycling After Thorne (1983)

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

Krimigis et al. Energetic Particle Recycling Mendillo et al. 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 Sodium

Jupiter Radio Emission Discovered in 1955

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

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

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

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

Alfven Wave Theory Gurnett & Geortz 1982 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.

Galileo Io Flyby Flow Magnetic field Electron Beams Galileo Fresh hot ions

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

Delamere et al. 2003Saur et al 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!

Delamere et al 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?

Ergun et al. Lessons from FAST at Earth

Ergun et al.

Su et al EARTH JUPITER 1-D Vlasov code

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

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

TORUS POWER How does UV power of the torus and aurora vary? TORUS POWER AURORAL POWER Oct Jan Apr Tera Watts

The Jupiter-Io system is a complex interconnected system. The Jupiter-Io System: The Big Picture Although the phenomena shown here have been well studied individually, the cause- and-effect relationships between them have not been established.

SMEX mission Earth- orbiting UV telescope to observe Io, the torus and Jovian aurora Trying Again!

JunoJupiterPolarOrbiter

Moving beyond initial exploration to address focused questions Challenging understanding of fundamental magnetospheric processes by exploring different parameter regimes Reconnection Cross-field diffusion Alfvenic acceleration Parallel electric fields Cross-scale coupling Momentum transfer Jupiter Polar Mission By testing our understanding of concepts developed at Earth through exploring the magnetosphere of Jupiter we open our eyes and see our own magnetosphere in a different light.

Galileo: The End Game Must never hit Earth 100 Rjupiter Sun Must never hit Europa Sent into Jupiter Sept. 21st 2003

Let’s Keep Exploring!