Whistler evidence of downward movement of ionization at low latitudes

The entire path of whistlers observed at our low latitude field station Nainital lies well within the upper boundary of the F-region. Large number of whistlers recorded during nighttime at Nainital show a smooth decrease in dispersion with time. This decrease in dispersion is interpreted in terms of corresponding decrease in the electron content of tubes of ionization. The computed result shows a downward flux of ionization at the base level of 500 km to be in the order of 2.8 X 108 electrons /cm2/sec.   It is also shown that the ambipolar diffusion alone cannot explain the transport of ionization in the topside F-region at low latitudes but some other processes such as E x B drifts are also important.