Observations of E-region field-aligned irregularities off the magnetic equator, using the Piura VHF radar

Abstract

We have used the Piura VHF radar (5°12'S, 80" 38'W, ~7.5" N geomagnetic latitude, just outside the magnetic equator) in northem Peru to gather echoes from 3-m E-region field-aligned irregularities (FAI). Similar irregularities have been intensively studied in the equatorial and auroral zones using ground-based radar systems and in-situ (rocket-bome) probes. Mid-latitude E-region FAI have been the subject of far fewer experiments over the years, however this situation is rapidly changing and multi-instrument experiments are being conducted and planned [1]. On the other hand at low-latitudes but outside the equatorial electrojet (EEJ), i.e., >±3", there have been not many radar observations, only those reported from a recent backscatter experiment in India [2], and the 1958 forward-scatter experiments in South America [3]. lt will be important to compare our radar observations to the better known irregularities at neighboring latitudes (equatorial and mid-latitude), in order to see the possibility of inferring sorne of the physical mechanisms goveming the off equatorial FAI. The Piura radar is part of a wind profiler network in the tropical Pacific. The main purpose of this system is to study the lower atmospheric dynamics. However, in order to observe the E-region FAI, we interrupt the normal operations of the radar. Coincidentally, we can do our observations by using one of the pre­defined antenna-pointing positions.