Effect of vertical drift on absorption and change in phase height of E-region reflections

The results of the simultaneous measurement of daytime absorption and of change in phase height, both at 2.2 MHz, have been used for the estimation of the peak vertical drift velocity and its location in the E-region. It has been found that like the measured hourly change in phase height the noontime values of the observed E-region absorption show significant departure from those expected for an undisturbed Chapman-alpha layer. Calculation shows that a peak drift velocity ranging between the extreme limits 44.0-2.20 m/sec and occurring around 2.5-3 km below the electron density peak of the Chapman layer may account for the observed departures of both change in phase height and absorption values. Considering some related observational data it is suggested that the drift velocity would be around 10-20 m/sec which is consistent with a value of alpha in the vicinity of 2.2-8.8 x 10 to the -8th cu cm/sec.