Low Dispersion Whistlers Observed Simultaneously at Two Low Latitude Stations

Employing the Haselgrove ray tracing equations and a diffusive equilibrium model of the ionosphere, the propagation characteristics of low dispersion whistlers observed simultaneously at low-latitude ground stations Gulmarg (geomag. lat. 24°10′N) and Naini Tal (geomag. lat. 19°1′N), are discussed. It is shown that these whistlers are caused by the VLF waves which were radiated from the return stroke of a lightning discharge, penetrated the ionosphere at two different entry points, propagated to the opposite hemisphere in the whistler mode and received at 19° and 24° geomagnetic latitudes. The lower and higher cut-off frequencies are explained in terms of their deviating away from the bunch of the recorded whistler waves.