The Earth is a huge magnet, and its magnetic influence extends far into space. Click here for a full size version of this image. In our everyday environment, magnetic forces are of no importance and a sensitive instrument, the compass needle, is needed to detect them. That is because we, the materials we encounter in everyday life, even the oxygen and nitrogen which we breathe, are all electrically neutral . The atoms of oxygen, for instance, contain electrons with negative electric charges and protons which are positive, but the two charges balance each other and make the atom as a whole electrically neutral.
Magnetic forces have almost no effect on neutral atoms.
These electrified fragments react strongly to the magnetic forces and can be steered and trapped by them. With a suitable input of energy, such fragments can also be accelerated to high speeds, can give rise to electic currents and emit a variety of radio-type waves. It follows that the structure of field lines near Earth determines much of the motion and behavior of the free electrons and ions found there.