Our previously developed nonlinear dynamical models of the magnetosphere exhibit deterministic chaotic behavior as the solar wind input which drives the systems increases from low to high levels. In this paper we employ the plasma physical analogue model (an extention of the damped, harmonic-oscillatory dripping faucet model) to consider explicitly the effect of time-varying the inputs. This works is equivalent to considering the effects of northward and southward turnings of the interplanetary magnetic field for various periods of time. We find that relatively extended episodes (≥ 2 hours) of turned on input with shorter (~1 hour) periods of turned off input lead to model behavior much like the continuously driven case. However, going to short input intervals with longer periods of zero input leads to highly irregular and dramatically fluctuating episodes of magnetotail unloading. These results give us insight into the diversity of apparent magnetospheric responses during relatively isolated substorm conditions. This work shows the absolutely critical interpendence (in a nonlinear dynamical system) of input phasing and internal magnetospheric response cycles. ¿American Geophysical Union 1991