Magnetic Fields Are Detected By
Magnetic Field: Moon
Lunar magnetic field is 107 times weaker than that of the Earth and lacks an internal dynamo
- Due to slow rotation and lack of fluid core.
- Localized regions of higher magnetic fields curious
- Solar wind directly impacts the surface.
- Creates a plasma void in the plasma umbra (perhaps the best vacuum in the solar system!)
Planetary Magnetic Fields: Venus
Venus as Earth's twin: Radius: 0.95 Mass: 0.81 Density: 0.95
We would expect similar magnetic properties to Earth.
Magnetic field of Venus is actually about 25,000 times weaker than Earth's.
Likely has a fluid core, so how can that be?........Slow Rotation!
Recall a dynamo requires a fluid core and rotation. Venus rotation period is 243 days.
- Solar wind is prevented from reaching surface by thick atmosphere.
- Bow shock results from interaction with ionosphere.
- No population of permanently trapped particles.
Weak magnetic field.
59 day rotation too slow for dynamo?
Bow shock, but no atmosphere.
Field too weak to contain particles.
Planetary Magnetic Fields: Mars
- Field 5,000 times weaker than Earth's.
- Solar wind interacts with ionosphere.
- 24.6 hr rotation fast enough for dynamo.
- RMars = 0.53REarth and No fluid core.
Magnetic Fields: Jupiter
- Enormous magnetic field (~20,000 times Earth's).
- Magnetosphere is ~1200 times larger than Earth's.
- Plasma derives from sulfur dioxide, hydrogen sulfide and other gases characteristic of Io!
- Detected from Earth as Synchrotron Radiation. A torus of plasma, coincident with Io's orbit.
- Aurora have even been imaged in Jupiter's atmosphere.
Galileo - first detection of a magnetosphere of a moon!
- Magnetosphere entry is noise 6-10 sec into recording.
- Pitch of tone indicates density of charged particles.
- Intermediate between Jupiter and Earth: 540X Earth's, 36X less than Jupiter's.
- Gas from Titan's atmosphere contributes nitrogen to the Saturnian magnetosphere.
- Saturnian satellites and rings absorb charged particles, making inner regions free of particles.
Planetary Magnetic Fields: Uranus
- Field strength is about 40X greater than that of Earth.
- Magnetic axis inclined 58.6o to rotation axis!
- Magnetic center offset from core by 30% of radius!
- Magnetic field strength ~1/4 Earth's.
- Magnetic axis inclined 50o to rotation axis.
- Magnetic axis offset 10,000 km from core (25% of radius).
Planetary Magnetic Fields: Pluto
- Small size and slow rotation (6.4 days).
- Suggests little/no magnetic field likely.