This figure shows a model of the Earth's magnetic field being generated within the Earth.
Click on image for full size
Gary A Glatzmaier (Los Alamos National Laboratory) and Paul H Roberts (University of California, Los Angeles).
Generating a Magnetic Field
Scientists think, although not certain, there are two essential ingredients for generating a magnetic field. Those two ingredients are
A bar of iron can be made into a magnet by wrapping it with wires and running a current through the wires.
It is believed a planet, or a star, can generate a magnetic field if it has both of the two ingredients above. It must have enough magnetic material, and it must have currents moving inside the magnetic material. If a planet does not have enough of either of these two ingredients, it will not have a magnetic field. Planets which do not have magnetic fields include Venus (moves very slowly), and Mars (most the iron is on the surface, and not molten).
You might also be interested in:
The force of magnetism causes material to point along the direction the magnetic force points. As shown in the diagram to the left, the force of magnetism is illustrated by lines, which represent the force....more
Unlike the Earth, which has a protective shield around it called the magnetosphere, the surface of the moon is not protected from the solar wind. This picture shows the magnetosphere surrounding the Earth,...more
The diagram to the left shows a cutaway of the possible inside structure of Ganymede, based on recent measurements by the Galileo spacecraft. It shows a small core of metal, overlain with some rocky material,...more
When the Galileo spacecraft flew by Ganymede, it found something that was a big surprise to everyone -- a very strong magnetic field. This is the first time a strong magnetic field had been found near...more
An important new result from the Mars Global Surveyor (MGS) mission is the definite confirmation of the presence of a magnetosphere around Mars. Previous missions did not make really good measurements...more
The Earth is a good example of a planetary dipole, where the lines of force point in a direction out of the South (magnetic) Pole and into the North (magnetic) Pole. Planets can also show evidence of quadrupoles...more
Earth has a magnetic field. If you imagine a gigantic bar magnet inside of Earth, you'll have a pretty good idea what Earth's magnetic field is shaped like. Of course, Earth DOESN'T have a giant bar magnet...more