Continuous measurements of nighttime electron concentration profiles and estimation of neutral wind velocities at Arecibo

Abstract

Results of continuous measurements of nighttime electron concentration profiles, using short pulses with the Arecibo incoherent scatter radar, are presented. The electron density distribution around the F₂ peak is found to be nearly a Chapman type and has a scale height which is the same as that of the neutral atmosphere. Vertical transport velocities are calculated from the time and the height gradients of the electron concentration, and the meridional neutral wind is deduced from these vertical drifts. The wind velocities are found to be positive most of the night and start decreasing rapidly before midnight. The velocities reach a very low value after about 0100 hours. The average maximum value of the velocity is about 100 m s^-1. On the average the equinox values seem to be higher than the summer values. These results are compared with those recently obtained from Doppler shift measurements at Arecibo.