Using airglow images observed at São João do Cariri (7.4ºS, 36.5ºW; dip angle: -11ºS) from September 2000 to April 2007, plasma bubblezonal drifts for ninety-seven geomagnetically quiet nights (Dst index higher than -30 nT) were calculated. The plasma bubble eastward averaged drifts presented an increase from 18:00 to 22:00 local time (LT), and followed by a deceleration. The plasma bubbles observed during high solar activity were faster after 22:00 LT. Eastward drifts observed during the summer, after 21:00 LT, were higher than drifts observed during the equinox months. Few nights had plasma bubble eastward drifts higher than 100 m/s and almost all bubbles disappeared after 02:00 LT. Averaged zonal drifts observed between -9.5 and -5.5ºS were almost constant, primarily,around 23:00 LT.
plasma bubble; airglow; ionosphere
