Electromagnetic Particles
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Planetary Magnetosphere
Earth's magnetic field acts like a giant dipole. Charged particles from the solar wind get trapped in this field, creating the Van Allen radiation belts. The particles undergo three simultaneous motions: fast gyration around field lines, slower bouncing between mirror points, and very slow drift around Earth.
Click and drag to inject particles with velocity
• Cyan = electrons (light, fast gyration)
• Magenta = protons (heavy, slow gyration)
• Gold = alpha particles (very heavy)
About This Simulation
This simulation demonstrates charged particle motion in electromagnetic fields using the Boris integrator, a second-order accurate, energy-conserving algorithm that’s the standard in computational plasma physics.
What You’re Seeing
- Cyan particles = Electrons (light, fast gyration)
- Magenta particles = Protons (heavy, slow gyration)
- Gold particles = Alpha particles (very heavy, slow gyration)
Particles spiral in the magnetic field at their cyclotron frequency: ω = qB/m
The radius of their circular motion is the Larmor radius: r = m v_⊥ / (|q| B)
How to Use
- Select field type: Uniform B field, magnetic dipole, or none
- Adjust field strength: Use sliders to change E and B fields
- Choose particle species: Select electron, proton, or alpha
- Click and drag: Inject particles with velocity from mouse movement
Physics Highlights
Energy Conservation: The Boris integrator maintains < 0.1% energy drift even after 10,000 timesteps in this demo.
Mass Matters: Notice how protons (1836× heavier than electrons) gyrate much more slowly in the same field.
Dipole Field: Simulates Earth’s magnetosphere - particles get trapped in the magnetic bottle!
Read the full technical article →
Performance: 100,000 particles @ 60 FPS. Built with Rust + WebAssembly.