Earth's magnetic field traps energetic protons (inner belt, ~1,000–6,000 km altitude) and electrons (outer belt, ~13,000–60,000 km) into doughnut-shaped regions that build intense particle flux over months to years.
A satellite only takes a dose hit while its instantaneous altitude sits inside a belt. Orbits that stay below the inner belt (LEO) or above the outer belt (GEO) largely avoid it; orbits that cross or linger inside a belt (slow-moving near apogee, per Kepler's second law) accumulate dose fast. This top-down view plots the same Kepler mechanics as the 3D scene, seen from above the orbital plane.
- Orange ring — inner proton belt.
- Purple ring — outer electron belt.
- Cyan path — the satellite's orbit, glowing where it currently crosses a belt.