Larmor Orbits: Charged Particles in a Magnetic Field

Plasma — the fourth state of matter — is a soup of free ions and electrons whose motion is dominated by electromagnetic forces rather than collisions. This simulator strips that behaviour down to its essence: a cloud of ions and electrons spiralling along magnetic field lines, exactly as they do inside a tokamak's confining field, in Earth's radiation belts, or in the solar wind. Each particle's velocity component parallel to the field is unaffected by the Lorentz force, while its perpendicular component rotates at the cyclotron frequency, tracing a helix whose radius — the Larmor radius — depends on the particle's mass, speed and the field strength. Turn up the magnetic field to watch every orbit tighten, raise the plasma temperature to see the spirals loosen, and add an electric field to reveal E×B drift: a sideways motion that carries ions and electrons together, in the same direction, independent of their charge — the mechanism that lets charged particles cross magnetic field lines in real plasmas.