Radio wave diffraction during the passage of an acoustic shock through a sporadic E layer

Bistatic HF Doppler measurements of the ionospheric disturbance arising from a large ground level chemical explosion have revealed a peculiar HF return which begins at large positive Doppler (> + 5Hz) and linearly evolves to large negative Doppler (< ‐ 5 Hz). Various pieces of evidence in our data suggest we observed an HF wave which is diffracted from the intersection of the acoustic shock and an extensive plane of sporadic E ionization at 110 km. From these measurements we estimate the horizontal trace velocity of the locus of intersection.