Simultaneous observations of some unusual whistlers and VLF hiss emission at a low L-value (LÂ =Â 1.17)

The purpose of this paper is to describe some unusual whistlers (doublets and triplets) and VLF hiss emission recorded simultaneously on February 18, 1998 during nighttime at a low latitude Indian ground station Jammu (geomag. lat., 22° 26′ N; L = 1.17), and to make some discussions about their origin. The detailed structures of the observed VLF hiss emission clearly show that these emissions confined to a narrow continuous frequency band. Some times the frequency of hiss band oscillates and subsequently touches the upper edge of the first whistler component of the doublet. Detailed structures of the dynamic spectra of whistler and VLF hiss emission are briefly presented. From the dispersion analysis of the whistler doublets and triplets, it is found that the individual whistlers of the doublets and triplets simultaneously observed on the same day are one-hop whistlers having propagation path along higher and closely spaced L-values. Our result also shows that VLF hiss has been generated in the equatorial region of higher L-values. Generation and propagation mechanisms are briefly discussed.