Quasi periodic echoes induced by a partial solar eclipse

The observations of mid-latitude quasi-periodic (QP) echoes during the partial solar eclipse on 22 July, 2009, using the MU radar at Shigaraki (34.85°N, 136.1°E) are presented. The rapid reduction in the E-region density, caused by the eclipse exposes the long-lived metallic ions within the Sporadic E-layers making it conducive for the gradient drift instability. These echoes resemble the normal post-sunset QP echoes observed over mid-latitudes. The present observations confirm that the mid-latitude Es plasma process is mainly controlled by density gradients. This example also reveals a hitherto unobserved aspect of mid-latitude ionospheric responses to eclipses.