Question

For Astronomy class, please answer this question clearly, thank you.

Describe the similarities and the differences between the mechanisms by which Terrestrial and Jovian planets generate their magnetic fields.

Answer 1

The planets in the solar system is divided into two groups :

i) The inner / terrestrial planets that include Mercury, Venus , Earth and Mars (have solid core)
ii) The outer/ Jovian Planets like Jupiter, Saturn, Uranus and Neptune

Planets like Earth, possess a solid core. The magnetic fields from such planets, therefore appear very similar to that of a bar magnet. Earth's magnetic field is tilted to about 18 degrees with respect to its rotation axis. Jupiter's magnetic field is characterized by a dipole moment that is 20 times larger than that of Saturn's. These planets ,like Earth, are oriented at approximately 10 degrees of the spin axis. While, Uranus and Neptune have highly tilted magnetic field that are offset. This implies that, the magnetic field for such planets do not resemble magnetic dipoles but more complicated structures. Thus, both Jupiter and Saturn posses strong magnetic fields while the magnetic fields of Uranus and Neptune possess irregular magnetic fields that are said to contain dynamos.

These dynamos create irregular magnetic fields. Neptune and Uranus a liquid core. One of the prime requisites for the dynamo model to function is that it requires a volume of electrically conducting fluid of likes of liquid Iron, metallic Hydrogen to carry "charge". A dynamo also needs a source of energy to drive convective motions in addition to the rotation of the planet.

Like terrestrial planets, (Earth, for instance), Jupiter also has episodes of aurora near its southern and northern hemisphere. But, a stark difference is that, the auroras in Jupiter are more intense and occur for a long duration, and sometimes they never stop. This can be attributed to Jupiter's intense radiations and its strong magnetic field. Also, the material from volcanoes from Io (one of the satellites of Jupiter) interact with the atmosphere of Jupiter (Ionosphere) to cause prolonged episodes of aurora.