It is used to study waves, instabilities and nonlinear behavior of tokamak fusion plasmas.
The distribution function depends on the three-dimensional position, the energy and magnetic moment.
The time evolution of the distribution function is described by gyrokinetic theory which simply averages the Vlasov-Maxwell system of equations over the fast gyromotion associated with particles exhibiting cyclotron motion about the magnetic field lines.
A Monte Carlo method is used to model small angle Coulomb collisions.
GEM is used to study nonlinear physics associated with tokamak plasma turbulence and transport.