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

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

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

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

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

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

Ganymede: A Magnetosphere within a Magnetosphere Torrence Johnson

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

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

Mars Global Surveyor Magnetometer - PI: M. Acuna

No core dynamo today Magnetization of surface rocks

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

Ionosphere

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

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

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

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

Mars’Interaction Boundary Response to the Solar Wind

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

Changing Topology of Mars’ Magnetic Field

Over a Strong Magnetic Region

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

Galileo Mission

The Galilean Satellites

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.

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

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!

Io 300 km Amirani

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

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

After Spencer & Schneider 1996

Plasma collides with atmosphere on the flanks

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

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

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

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

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

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

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.

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

Juno Jupiter Polar Orbiter ~$650M

Solar Wind Interaction with a Comet

Comet Borelly ENERGY Heavy Ions H+ TIME

Deep Space 1

Pluto & Charon

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

Thank you! New Horizons 2016