The image above is taken from the BBC sciences pages and shows the Van Allen Belt, which is the magnetic shield that surrounds the earth and protects the planets from harmful radiation carried on the solar wind.

I thought I would make it clear to the reader that a planet can have an electromagnetic gravitational field and yet not have such an electromagnetic shield. An example of this is Venus, which has a gravity field but does not have any protective magnetic shield. A gravity field and the magnetic radiation shield are two different phenomena.