Three high-explosive charges were placed by rocket in the lower E layer to study the effects of detonation waves on this region of the ionosphere. Observations made by coherent-pulse-Doppler high-frequency radar and an ionosonde indicated that three types of radar targets were discerned: (1) Shock-wave excitation of atmospheric constituents and compression of existing ionization created an overdense reflecting surface, with a probable small additional contribution due to partial reflections, that traveled radially outward quite rapidly and was observed for a few tenths of a second. (2) Shock-induced ionization created as a result of the high temperatures achieved in the region between the first shock wave and the contact surface between the explosion products and the atmospheric fluid persisted as a nearly stationary radar target for several minutes. (3) Sonic waves propagating outward from the detonation were observed to perturb sky-wave transmission paths that passed through the ionosphere many tens of kilometers from the explosion. These effects were detected several minutes after the explosion. It is concluded that explosive thermal excitation of the lower E layer is adequate to produce radar reflections of decameter wavelengths by compression of existing ionization and shock excitation of additional ionization and to deposit by this means long-lasting ionization, which may appear as an artificial sporadic-E layer of several minutes duration. This layer is probably composed of the long-lived ions of alkali metal atoms, which exist continuously in the lower E region and form a detectable persistent radar target when they are excited by a shock wave. This result and other workers' independent evidence for atmospheric acoustic-wave effects in the lower E region indicate that such phenomena may be involved in the growth of naturally occurring sporadic-E layers. The sonic wave created by the explosion also perturbs existing ionospheric regions several tens of kilometers from the burst point, and this perturbation is readily detectable as a phase-path modulation in decameter-wavelength earth backscatter.