Generation and propagation mechanism of low latitude VLF emissions

Abstract

The generation mechanism of VLF emissions observed in the low latitude ground station is studied by calculating the energy and growth rates for different pitch angles at <i>L</i>=l.2, 1.5 and 1.8 in cyclotron and Landau resonance mechanisms. The results show that the required energy of the electrons is much higher in cyclotron resonance mechanism than in Landau resonance mechanism and the growth rates are positive in both the cases. Since the highly energetic electrons with large pitch angles are available at the lower edge of the inner radiation belt, it is inferred that cyclotron resonance is responsible for the generation of these emissions. The Landau mechanism may possibly be responsible for off-equatorial resonances. The propagation paths of these emissions are discussed in terms of non-ducted mode of propagation.