Statistical characteristics of VHF radar observations of low latitude E-region field-aligned irregularities over Gadanki

Abstract

The statistical characteristics of E-region field-aligned irregularities observed with the Gadanki MST radar are presented and compared with observations made with the Piura radar at a similar magnetic latitude. Echoes are observed day and night, with the nighttime echoes being more intense and covering a greater height extent than during the day. The most probable echo occurrence times are just after sunrise (95%) and just before sunset (80%), when the echoing regions were centered around 95 and 100 km, respectively. The lowest probability of echo occurrence is found to be during noontime hours. The spectra of these echoes over Gadanki were all type 2. The mean Doppler velocities for altitudes above 105 km were upward at typically 10ms^-1 during the day and downward at about during the night. Spectral widths of 10-40ms^-1 were found during the day and 30-60ms^-1 during the night. These characteristics of E-region irregularities over Gadanki are quite similar to those found over Piura, and are remarkably different from those at either equatorial or higher latitudes.