The power spectrum analysis of the occurrence rate of whistlers
observed at Varanasi (geom. lat. 14o 55' N) shows
periodicity
of the order 70-80 min which has been interpreted as the lifetimes of the
ducts trapping and guiding the whistlers. This is also corroborated by the
dispersion analysis of the recorded whistlers. The observations clearly
favour
the existence of large numbers of ducts simultaneously. The analysis
shows that these whistlers had propagated in the magnetosphere along
higher L-values (L = 2.1-2.7)