Computer artwork showing the radiation belts (green) - two doughnut-shaped (torus) regions full of high-energy particles - that fill the near-space around Earth. The blue and red lines between and around the belts depict the north and south polarity of the planet's magnetic field. The inner belt, a blend of protons and electrons, can reach down as low as 1,000 kilometres in altitude. The outer belt, comprised mainly of energetic electrons, can swell to as much as 60,000 kilometres above Earth's surface. Both rings extend to roughly 65 degrees north and south latitude.