Magnetospheric sawtooth oscillations are observed during strong and
steady solar wind driving conditions. The simulation results of our
global MHD model with embedded kinetic physics show that when the total
magnetic flux carried by constant solar wind exceeds a threshold,
sawtooth-like magnetospheric oscillations are generated. Different from
previous works, this result is obtained without involving time-varying
ionospheric outflow in the model. The oscillation period and amplitude
agree well with observations. The simulated oscillations cover a wide
range of local times, although the distribution of magnitude as a
function of longitude is different from observations. Our comparative
simulations using ideal or Hall MHD models do not produce global
time-varying features, which suggests that kinetic reconnection physics
in the magnetotail is a major contributing factor to sawtooth
oscillations.