Forum:Planetary magnetic fields
Some thoughts on Planetary Magnetic Fields, and their effect and implications.
They can shield the planets atmosphere from the local stellar wind, which would otherwise erode/deplete the planets atmosphere. They can shield the surface of the planet from alpha and beta particle emissions from local stellar bodies.
By protecting the atmosphere, they maintain the surface pressure at a level consistent with the planets size, which in turn may prevent water or other liquids from sublimating to a gas.
- So small to medium wet planets would usually have a strong magnetic field.
In short, a healthy magnetic field protects the planet, its atmosphere, and it's inhabitants.
- Small to medium sized Planets with a thin atmosphere may have their thin atmosphere due to a weak or non-existent magnetic field.
Likewise, Small to medium sized Planets having a good thick wet atmosphere are likely to have a strong healthy magnetic field.
We may also infer other information about planetary geology from the planetary magnetic field.
- A strong magnetic field implies that the planet has a hot core (i.e. liquid magma, with a very hot metallic inner core).
This is the most likely mechanism for generation of a planets magnetic field.
A weak magnetic field may exist after a planet has completely cooled, but such a field should be orders of magnitude weaker than that of a similarly sized planet with a hot active core.
An energetic core also effects the geologic or tectonic activity of the planet.
- A hot active core is much more likely to generate vulcanism (active volcanoes) and possibly geological plate tectonics.
A cold core planet may have quakes (due to gravitational or other stress), but not vulcanism.
- 21:37, 16 September 2014 Fomyers
Another implication is that a planet with a magnetic field has a significant radiation belt. Terra's has two belts an inner one starts between 200 and 1000km above the surface and extends to about 2 planetary radii. The outer belt starts at about 4 planetary radii and extends to about 8 planetary radii. The inner belt (less than 2 radii) has particles of 100MeV (occasionally 400MeV) (able to penetrate 14cm of Lead) while the rest is limited to about 10MeV. Each passage through the belts accumulated about 1 rad on NASA astronauts. This suggests that each space-combat turn you linger in the belt, the ship gets 1 rad of exposure. Caution, the outside of your ship can become seriously radioactive!
Jupiter's radiation belt is between 45 and 100 times the planetary radius and includes the orbit of Io.