The Magnetosphere of Jupiter

New Perspectives from Galileo and Cassini

Fran BagenalUniversity of Colorado

TitleThe Magnetosphere

of Jupiter

New Perspectives from Galileo and Cassini

Fran BagenalUniversity of Colorado

Comparative Magnetospheres

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

Compressibility

Earth ~ Dipole

Rmp ~ (V2)-1/6

Jupiter

Rmp ~ (V2)-1/3

solar wind V2

solar wind V2

10 RE

100 RJ

compress 2Earth ~ Dipole

Jupiter

solar wind V2

solar wind V2

Rmp -> 0.5 Rmp

Rmp -> 0.7 Rmp

Factor ~10 variations in solar wind pressure at 5 AU -> observed 100-50 Rj size of dayside magnetosphere

7 RE

50 RJ

~10

<<1

= nkT B2 /8

IoGanymede Europa

Callisto

1 ton / sec

Galileo Mission

Galileo Spacecraft

spins 3 rpm

Cassini flybyDec. 2000

Galileo Orbiter33 orbitsDec. 1995 to Sep. 2003

Voyagers

Pioneers

Ulysses

SolarWind

Magnetopause

SOLAR WINDRotation + Outflow

SolarWind

EARTHSolar Wind Driven Convection

Strong magnetic field10 hour rotation periodInternal plasma source

Equatorial plasma diskCorotation with JupiterSlow 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, & JetsDisks, 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 RJ

• 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

Ganymede Europa & 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

GalileoNIMSIR 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. 1997

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, SO2, S2..? ~1 ton/s ~3 x 1028 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 1012 W

Cold Torus: Ne~1000 cm-3 S+

Ti~Te~1 eV Local Io Source? ~20%?

UV

Io Plasma Torus (Schneider & Trauger)

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 tiltE W brighter

Io Plasma Torus

Wavelength

Image of Torus in O+ EmissionS++ Emission Jupiter’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?T

era

Wat

ts S+++

O+O+

S++

S+++

S+

Oct Jan Apr 2000 2001

1 2 3Steffl

Models of Torus Chemistry

Neutral Cloud Theory:Source = atomic O, SIonization, Charge Exchange, RecombinationRadiative CoolingIon-Electron coupling - Coulomb collisions

Electron heating: Necessary to provide UV emitted powerUsually specified as Fhot=Nehot/Necold and

Thot

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+ +

• 50-80 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 hoursJupiter’s Radio Emission Controlled by - Location of Io - Magnetic Longitude

Io Phase

Longitude

BA A

B

AB

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. 1983

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 - 1995

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. 2002

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. 2003

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. 2003

EARTH

JUPITER

1-D Vlasov code

Aurora

Io footprint

Io w

ake

Main Oval

Polar storms- Solar Wind Generated?

Dusk Distortion?

Clarke et al.

AuroraThe 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 2000 2001

Ter

a W

atts

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!

JunoJunoJupiter Jupiter Polar Polar

OrbiterOrbiter

• 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!Let’s Keep Exploring!