Analysis of Doppler Velocities of Equatorial Electrojet Type 1 Irregularities

摘要: Equatorial ionosphere observations using VHF radars show backscattered echoes from electron density irregularities in the equatorial electrojet (EEJ). The studies of the echoes have revealed distinct spectral signatures of two types of irregularities, named type 1 and type 2, explained by the modified two-stream and the gradient drift instabilities, respectively. Type 1 echo spectra normally presents a sharp peak centered at around 120 Hz for 50 MHz radars, which corresponds to a Doppler shift of about 360 m/s (close to the ion-acoustic speed). Several experiments have been done to investigate the EEJ irregularities in order to characterize its phenomenology using RESCO 50 MHz radar at the Brazilian sector. In the present work we summarize some characteristics of type 1 echoes based on power spectra of backscattered signals from 3-m EEJ plasma irregularities. We also show statistics of its occurrence in simultaneous height and time, including a velocity distribution analysis.