For instance, flows of molten metals deep inside Earth's core cause currents which sustain a huge magnetic field that extends far into space. As seen in the diagram at left, magnetic fields are represented by lines of force. Earth's magnetic field lines spread out from the south polar region and come together in the north polar region. Understanding how plasmas interact with electric and magnetic fields gives us a better idea of what is happening between the Sun and Earth and elsewhere in the universe, but many mysteries remain. For over 30 years, scientists and engineers in many different countries have tried to create a fusion reactor that produces more energy than it consumes.
All atoms have a dense nucleus.
Fission and fusion reactions are two ways a nucleus changes. The plasma discharge inside Princeton's Tokamak Fusion Reactor. The excess energy can be used to operate a nuclear power plant or in a more sinister way it can produce the incredible energy in a nuclear explosion. A fusion reaction, on the other hand, occurs when hydrogen nuclei collide and form a heavier nucleus like helium. The only fuel required in a fusion reactor is the heavy hydrogen found in seawater, a virtually limitless source of energy.