Fig. 8

Band-pass filtered oscillations in F layer height at 8 MHz over Cachimbo, from midday to midnight, mass plotted for a group of days (top). Note the near coherence of the oscillation phase on these days. Oscillations show random phases, (middle). The gray segments of the individual curves (during night hours) represent spread F occurrence. The F layer vertical drifts averaged for the two groups of days, the red and blue curves corresponding to the first group and second group, respectively, (bottom)