We demonstrate, using a simple model, that high intensity pulses can be generated, by making use of the dispersive properties of the ionosphere, from a modifier of much lower intensity whose frequency is a parabolic function of time. We show that such a frequency-chirped pulse can be constructed so that its various components overtake each other at a prescribed height, resulting in large (up to one hundred times) transient intensity enhancements as compared to those achievable from a steady modifier operating at the same power. We examine briefly one possible application: the enhancement of plasma wave amplitudes which occurs as a result of the interaction of such a compressed pulse with pre-generated turbulence. ¿ American Geophysical Union 1993