The plasma and the neutral gas inside the channel is strongly heated by the current flow. This causes a sudden expansion of the lightning channel which can be heard as thunder. It could only recently be proved that lightning discharges occur between cloud and ionosphere . The direction of the Lorentz force is perpendicular to those of the magnetic field and the velocity. Magnetic confinement Common name for plasma confinement in a tokamak or stellarator .
Inertial confinement is used in laser fusion , whereas stars use gravitational confinement.
In a magnetic field charged particles are forced by the Lorentz force to move on helical orbits. In cases where the magnetic field lines form a converging bundle, the average Lorentz force possesses a component that points towards the region of weaker magnetic field. Therefore particles are reflected in regions of converging magnetic field lines such as close to the magnetic poles. By this mechanism energetic particles are trapped in the radiation belts . Magnetosphere The pressure of the impinging solar wind compresses the magnetic field of the Earth on the sunward side and extends it on the midnight side into a long tail.