A detailed study of the diamagnetic properties of magnetospheric plasma injected at synchronous altitudes is presented. Defining the magnetic induction field B=H+4&pgr;M, we have computed the magnetization M from the plasma distribution functions and show that the diamagnetic contribution of the particles having energies of ~100eV to 81 keV can completely account for observed changes in the magnetic induction energy density. Computation of the resulting magnetic field H indicates that the current system in the magnetosphere is complex. Significant changes in H have been observed in a feq minutes time scale. Studies of the particle density at various magnetic moments show that both protons and electrons together or individually act to cause the diamagnetic variations in B.