Energy-preserving methods for guiding center system based on averaged vector field

Abstract

We propose a family of energy-preserving methods for guiding center dynamics by perceiving its Hamiltonian nature based on the averaged vector field. The energy conservation, symmetric property, and algebraic order of these methods are studied. Furthermore, higher order energy-preserving methods are systematically introduced by using a composition technique. Two second order and two fourth order symmetric energy-preserving methods are constructed and applied to simulate the guiding center motion in both the dipole magnetic field and the tokamak magnetic field. Numerical results show that these methods have significant superiorities in energy conservation compared with the existing canonicalized symplectic methods of the corresponding orders. The numerical case of the guiding center motion in the toroidal acceleration electric field exhibits favorable long-term conservative properties of the new methods to the particle-field system, while the kinetic energy of guiding centers keeps increasing. These energy-preserving methods based on the averaged vector field can be applied to any non-canonical Hamiltonian system.