Particles

Species

Proton (inner belt) Electron (outer belt)

Particle count: 120 L-shell of injection: 2.0 R_E Pitch angle α: 60° Sim speed: 1.0×

Display

Show field lines Show belt density Show loss cone

Stats

Trapped0

Lost (cone)0

Pitch α60°

Loss-cone α_lc—

Bounce period—

Drift—

Earth's dipole field traps charged particles on helical paths. They spiral around field lines, bounce between mirror points and drift around the planet — populating the inner (protons) and outer (electrons) Van Allen belts. If the equatorial pitch angle α is smaller than α_lc, the mirror point is below the atmosphere and the particle is lost.