The
Magnetosphere
The Magnetosphere
Title of
of Jupiter
Jupiter
New
New Perspectives
Perspectives from
from
Galileo
Galileo and
and Cassini
Cassini
Fran
Fran Bagenal
Bagenal
University
University of
of Colorado
Colorado
Comparative Magnetospheres
Testing our understanding of SunEarth connections through
application to other planetary systems
Earth ~ Dipole
Rmp ~ (rV2)-1/6
Compressibility
10 R
E
solar wind rV2
Jupiter
Rmp ~ (rV2)-1/3
100 RJ
solar wind rV2
Earth ~ Dipole
Rmp -> 0.7 Rmp
compress
2
7R
E
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
b <<1
b ~10
b = nkT
B2 /8p
Ganymede
Io
Europa
Callisto
1 ton / sec
Galileo
Mission
Galileo Spacecraft
spins 3 rpm
Voyagers
Pioneers
Solar
Wind
Galileo
Orbiter
33 orbits
Dec. 1995 to
Sep. 2003
Cassini flyby
Dec. 2000
Ulysses
SOLAR WIND
Rotation + Outflow
EARTH
Solar Wind Driven Convection
Solar
Wind
Strong magnetic field
10 hour rotation period
Internal plasma source
Equatorial plasma disk
Corotation with Jupiter
Slow outward transport
Jupiter - Momentum Coupling
• As plasma from Io flows
outwards its rotation decreases
Khurana 2001
(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
Disks, B, Stellar Rotation, & Jets
John Bally
Global Structure & Dynamics
• Galileo - Survey of magnetic field in the equator
-> structure and current systems
Jupiter-like
Rotation
modifies
structure at
Jupiter
Earth-like
Khurana 2001
Global Structure & Dynamics
Flow Pattern in the Equator
• In situ plasma measurements
Bursts
Superrotation
EPD data
• Rotation dominates to >140 RJ
Krupp et al.
• Local time asymmetry
• Observed flow pattern consistent
with MHD simulations but ~1.5
times stronger.
• Abrupt bursts
MHD simulation
Ogino et al.
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
Satellites in the Magnetosphere
Ganymede
Europa & Callisto
• Dynamo in iron core
• Magnetosphere within a
magnetosphere
• Radiolysis of surface
Galileo
NIMS
IR image
• Currents induced by changing
field indicate liquid water layer
Io
300 km
Amirani
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
Io’s
Volcanoes
& Geysers
Pilan Plume
Prometheus
Pilan 5 months apart
Pele
InfraRed
Galileo - Nightside of Io - Visible
Glowing Lava
Plume Gas
& Dust +
Aurora
After Spencer & Schneider 1996
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
UV
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
Source:
Extended clouds
O, S, SO, SO2, S2..?
~1 ton/s ~3 x 1028 ions/s
Dn/n~2% per rotation
Local Io Source? ~20%?
Io Plasma Torus (Schneider & Trauger)
S+
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
E
= direction of dipole tilt
W brighter
S++
Emission
Image of Torus in O+ Emission
Jupiter’s Aurora
110°
200°
290°
Wavelength
Steffl
How do composition, temperatures and UV power vary?
Cassini UVIS
Steffl
600A
1900A
How do composition, temperatures and UV power vary?
Steffl
1
3
Tera Watts
2
S+++
S++
O
O++
S+++
S+
Oct
2000
Jan
2001
Apr
Models of Torus Chemistry
Neutral Cloud Theory:
Atomic data issues
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
Energetic Particle Recycling
After Thorne (1983)
3Energetic
- Energetic
Particle
Particle
Recycling
Recycling
After Thorne (1983)
Energetic Particle Recycling
• Energetic Neutral Atoms charge exchange
S+ + O -> O+ + S*
Cassini MIMI
• 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?!
Krimigis et al.
Energetic Particle Recycling
Extended Fast/Energetic
Neutral Wind
• Sodium - ground-based
telescopic observations of
scattered sunlight - cold
neutral wind from chargeexchange of torus ions
Sodium
Mendillo et al.
•MIMI observations of hot
neutral sulfur and oxygen
(molecules?) from chargeexchange of radiation
belt particles >2 AU away
Krimigis et al.
Jupiter Radio Emission Discovered
in 1955
Early Discoveries
Io Phase
B
A
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
Early Explanations
Goldreich &
Lyndon-Bell
(1969)
Dulk (1965)
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
Voyager Radio Discoveries
Voyager PRA
Warwick et al. 1979
• Repeated patterns of
arcs in frequency-time
spectrographs
Carr et al. 1983
• Indicates systematic
beaming pattern,
controlled by the
geometry of Jupiter’s
magnetic field.
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.
Gurnett & Geortz 1982
• Nice idea—but probably
little wave power reaches
high latitudes.
Galileo Io Flyby - 1995
Fresh hot ions
Galileo
Electron Beams
Connerney et al.
The Io Aurora
Infrared
Io
Ultraviolet
- energetic particles bombard atmosphere
- ‘wake’ emission extends halfway around Jupiter
Clarke 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!
Saur et al. 2002
Delamere et al. 2003
What happens between the torus and
Jupiter where the density is very low?
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 nonuniform background
plasma
Delamere et al. 2003
Lessons from
FAST at Earth
Ergun et al.
Ergun et al.
EARTH
Su et al. 2003
JUPITER
1-D
Vlasov
code
Clarke et al.
Aurora
Dusk Distortion?
Polar storms
- Solar Wind Generated?
Main Oval
Io footprint
The aurora is the
signature of
Jupiter’s attempt
to spin up its
magnetosphere
Aurora
Clarke et al.
How does UV power of the torus and aurora vary?
Tera Watts
TORUS
TORUSPOWER
POWER
AURORAL POWER
Oct
2000
Jan
2001
Apr
The Jupiter-Io System: The Big Picture
Although the
phenomena shown here
have been well studied
individually, the causeand-effect relationships
between them have not
been established.
The Jupiter-Io system is a
complex interconnected
system.
SMEX
mission
Trying Again!
Earthorbiting UV
telescope to
observe Io,
the torus and
Jovian
aurora
Juno
Jupiter
Polar
Orbiter
Jupiter Polar Mission
• 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
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
Sun
• Must never hit Earth
• Must never hit Europa
• Sent into Jupiter Sept. 21st 2003
100 Rjupiter
Let’s Keep Exploring!