  In this paper, by the use of the topological current theory, the topological
structures and the dynamic processes in thin-film ferromagnetic systems are
investigated directly from viewpoint of topology. It is found that the
topological charge of a thin-film ferromagnetic system can be changed by
annihilation or creation processes of opposite polarized vortex-antivortex
pairs taking place at space-time singularities of the normalized magnetization
vector field of the system, the variation of the topological charge is integer
and can further be expressed in terms of the Hopf indices and Brouwer degrees
of the magnetization vector field around the singularities. Moreover, the
change of the topological charge of the system is crucial to vortex core
reversal processes in ferromagnetic thin films. With the help of the
topological current theory and implicit function theorem, the processes of
vortex merging, splitting as well as vortex core
