Equatorial quasiperiodic echoes from field-aligned irregularities observed over Jicamarca

Abstract

This is a report of so far undescribed equatorial quasiperiodic (EQP) echoes from field-aligned irregularities from the E and lower F region. These echoes were observed on October 20, 1993 at the Jicamarca Radio Observatory in conjunction with a spectacular spread F event. We have identified two regions where striated EQP echoes are clearly observed. The time periods are between 1 and 5 min. In the first region (120–140 km) the slope of the striations is negative (apparent downward propagation), while in the second (160–200 km) the slope is positive. Moreover, in the first region the time periods (striation spacings) are smaller and the altitude rates of change are higher than those observed in the second region. Although these equatorial echoes appear somewhat similar to those seen at midlatitudes, we believe that the two phenomena are different. We have no explanation as yet for these EQP observations; our purpose in presenting these data is primarily to describe their properties in more detail than has been done in the past.