Hook Whistler—a New Equatorial Whistler observed by Injun 3

Attenuation of lightning‐produced sferics in the Earth‐ionosphere waveguide and low‐latitude ionosphere

“…[3] The wave dispersion is a function of the wave frequency, the ionosphere's electron density, the magnitude of the Earth's magnetic field, and the orientation of the whistler wave vector to the background field [Helliwell, 1965]. In situ study of these oblique whistler waves goes back decades, with observations of multipath whistlers [Gurnett et al, 1966] and interference bands from harmonics of the ion gyrofrequency [Shaw and Gurnett, 1971] by the INJUN satellite. Further study by the DE (Dynamics Explorer) satellite indicated a connection between lightning whistlers and ionospheric hiss [Sonwalkar and Inan, 1989].…”

Hook whistlers observed at low latitude ground station Varanasi

“…lat., 16~ originally believed to be within some sort of a low latitude cut-off was reported by Singh et al (1977). A new type of whistler called the hook whistler which was earlier reported by Gurnett et al (1966) from very low frequency radio noise data from the Injun-3 Satellite, was however successfully recorded for the first time at Varanasi by Singh et al (1981) during their routine ground based measurements. Gurnett et al (1966) interpreted the observed hook whistler in terms of two electron whistler arising out of one single lightning impulse and travelling along two different propagation paths so as to converge at the receiving satellite.…”

“…The simultaneous differential equations used for the ray path computation are similar to those of Haselgrove (1955), Yabroff (1961), Kimura (1966) and Shawhan (1966). In the present investigation, only two dimensional case is considered.…”

“…The electron density at the reference level of 400 km is taken from Alloutte I observations corresponding to our low latitude. The night time oxygen and helium densities and the temperature corresponding to the reference level are taken from the analysis of incoherent back-scatter spectra gathered over the period 1965-1967(Prasad, 1968 and the fractional concentration of hydrogen ions is taken from the night time Injun-3 proton whistler analysis (Shawhan and Gurnett, 1966). The details of the model are as follows: P.N.…”

“…A new type of whistler called the hook whistler which was earlier reported by Gurnett et al (1966) from very low frequency radio noise data from the Injun-3 Satellite, was however successfully recorded for the first time at Varanasi by Singh et al (1981) during their routine ground based measurements. Gurnett et al (1966) interpreted the observed hook whistler in terms of two electron whistler arising out of one single lightning impulse and travelling along two different propagation paths so as to converge at the receiving satellite. A comprehensive theoretical investigation of hook whistlers detected by Gumett et al (1966) from Injun-3 satellite observation was carried out by Shawhan (1967) using ray tracing technique.…”