The Magnetism of
Jupiter:
Erupting Volcanoes and
Dazzling Auroras
Fran Bagenal
University of Colorado
Earth
Rock
Liquid
Iron
Solid
Iron
Earth
Planetary
Rotation
Earth's magnetic
field
is generated in
the liquid iron
outer core
Vigorous motions in electrically
conducting liquid iron
Solar
Wind
Magnetosphere
Jupiter - "The Gas Bag"
A Giant Ball of Hydrogen
Thin "weather" layer
Mass of Jupiter
~320 x Earth
Gravity
Rock/Iron Core
Low pressure
Gas/Fluid
Mass of Jupiter
~320 x Earth
Electrically
Conducting
Fluid
High pressure
Gravity
Pressure ~50-70 Million Bar
Jupiter
•Large volume of
conducting fluid
•Rapid rotation
•Strong magnetic
field
20,000 x stronger
than Earth
Earth
Jupiter
Both magnetic
fields are tilted
~10° from the
planet's spin axis
Earth
Magnetosphere
Solar
Wind
~10 Earth Radii
Earth
Jupiter's strong
magnetic field
makes a vast
magnetosphere
~100 Jupiter Radii
1000 Suns would fit inside Jupiter's magnetosphere
James Van Allen's
Discovery of the
Radiation Belts
Explorer 1
1957
Radiation
Belts
Energetic protons
and electrons
trapped by the
Earth's magnetic
field
Jupiter
Very
Large
Array
Radio
Telescope
Intense radiation
belt revealed by
radio emissions
Cassini
Jupiter
Scale, rotation-dominated, Io
source
Galileo
1610
Ganymede Io
Europa
Callisto
The Galilean
Satellites
Galilean Satellites
Orbital Resonance
4
2
1
Tidal forcesincrease strongly closer to Jupiter
•Heat the interior
•Remove water
•Drive volcanic activity
Rock + Iron
Io
3.57 g/cc
Ganymede
1.94 g/cc
Europa
2.97 g/cc
Callisto
1.86 g/cc
Ice + Rock
Ganymede:
Magnetosphere within a Magnetosphere
• Only moon with a magnetic field
• Size and strength similar to Mercury
Io
Amirani
300 km
Io’s
Volcanoes
& Geysers
Pilan Plume
Prometheus
Pilan 5 months apart
Pele
IR
Tvashtar
New Horizons data - Feb. 2007
Title
Io
Plasma =
hot,
ionized
gas
~3 Million Amps
Electrical Currents
Magnetospheric plasma interacts with
Io's atmosphere
Io Plasma Torus
Total mass ~ 2 Megaton
Source ~1 ton per second
Replaced in ~25 days
The
Magnetosphere
Title
of Jupiter
New Perspectives
from Galileo and
Dense plasma from Io spreads out to fill the giant magnetosphere
Coupled to spinning Jupiter by the magnetic
field
Cassini
Fran Bagenal
University of Colorado
Jupiter's 3 Types of Aurora
Steady Main
Auroral Oval
- Associated with
spinning plasma
sheet
Aurora associated with moons
Variable
Polar
Aurora
- Caused by
what??
Juno
Jupiter’s 3 Auroras
1. Main Aurora
2. Polar Aurora
3. Io Spot + Wake
Hubble
Space
Telescope
Shown in magnetic
coordinates - rotating
with Jupiter
To explore Jupiter’s poles – and sending..
deep interior – NASA is
Juno
Microwave Radiometer
Magnetometer
Energetic Particle
Detector
Plasma Detector
Plasma Waves
UV Spectrometer
Launch 2011
Arrive 2016
Juno:
First to fly
over the poles
Juno
Juno passes directly
through auroral field lines
Measures particles
precipitating into
atmosphere creating aurora
UV images of the aurora
How does the system
actually work?
Thank you