We review basic mechanisms of magnetospheric dynamics taking the cases of Ganymede, Mercury, and Jupiter. The topics include; (1) Whether or not possible effect of the intrinsic time variability of the reconnection rate can be seen in Ganymede's magnetosphere which is embedded in an almost fixed magnetic field of Jupiter. (2) How well the occurrence of reconnection is observationally founded for Mercury's magnetosphere. (3) In what ways various types of Jovian aurora are related to specific features of magnetospheric dynamics. (4) By what mechanisms solar wind influences the activity of the Jovian magnetosphere. (5) How the energetic particles are supplied to the boundary region of the Jovian magnetosphere and escape to the interplanetary space keeping high energies.