Imaging coherent scatter radar, incoherent scatter radar, and optical observations of quasiperiodic structures associated with sporadic E layers

Abstract

During June and July 2002, a 30‐MHz imaging coherent scatter radar was installed and operated on the island of St. Croix, to view the E region ionosphere above Arecibo, Puerto Rico. During the observing period, 10 events with discernible quasiperiodic echo structure were observed with the coherent scatter radar. In six of those events, simultaneous measurements were made with the Arecibo 430‐MHz incoherent scatter radar. The imaging coherent scatter radar allows us to locate and track the echo structures within the volume illuminated by the transmitter, which shows structures that are generally aligned along wavefronts. A slight preference for motion of the structures toward the southwest is evident throughout the period, but the propagation directions and speeds vary greatly. The incoherent scatter radar measurements show a close correspondence between the occurrence of the coherent echoes and the location of the enhanced electron density structures. In particular, the coherent echoes occur when the electron density layers show uplifts.