Low-latitude quasiperiodic echoes observed with the Piura VHF radar in the E region

We present the first quasiperiodic (QP) echoes from 3-m E region field-aligned irregularities observed in the Southamerican sector, just outside the magnetic equator (7.5 degrees N geomagnetic). These QP echoes occur only at night and between 105 and 120 km. In general, Piura QP echoes present periods close to the Brunt-Vaisala period (5 to 10 min), striations with positive slopes and altitude rates of 20-25 m s(-1) (upward/northward), striations spacings of 3 to 10 km, and downward/southward Doppler velocities. These results are compared to midlatitude QP echoes from 3- and 6-m irregularities observed between 13.3 degrees N and 46.7 degrees N geomagnetic. We found that the general characteristics that are common to our observations and other QP observations are the nighttime occurrence and the periods close to the Brunt-Vaisala period. On the other hand, the discrepancies with some of the QP echoes observed at midlatitudes are found in the slope and spacing of the striations, the mean phase velocities, and the mean altitude location of the E layer containing the striations.