In an atomic gas, the motion of particles (atoms) is governed by the collisions. If the gas is ionized, then the motion of created particles may be mainly governed by

In a neutral atomic gas, the atoms are electrically neutral, and their motion is primarily determined by short-range mechanical collisions. When the gas is ionized, it enters the plasma state, which consists of free electrons and ions. Since these particles carry an electric charge, they interact through long-range electromagnetic forces (Coulomb forces). In such a medium, the collective behavior and trajectories of the particles are dominated by these electromagnetic interactions rather than simple binary collisions. Gravitational forces are far too weak to govern motion at the atomic scale, and scattering is itself a result of the electromagnetic interactions between the charged particles.