Earth's radiation and plasma belts. Computer graphic showing the Earth's radiation belts (outer, multi-coloured) and plasmasphere (blue-green). The shape of these structures are largely determined by Earth's dipole magnetic field (curved lines). Within the radiation belt, charged particles are confined and spiral around magnetic field lines. Yellow lines represent negatively-charged electrons. Blue lines represent positively-charged ions. The cooler plasma of the plasmasphere keeps higher-energy particles outside its boundary, called the plasmapause.