On the ground observation of whistlers at low latitudes

Abstract

By employing Haselgrove equations and a diffusive equilibrium model for the electron‐ion density distribution in the ionosphere, ray‐tracing computations are carried out to study the propagation characteristics of whistler waves observed in the low‐latitude ground stations. It is shown that such waves are propagated in the ionosphere in the prolongitudinal mode of propagation under the influence of suitable negative latitudinal gradients of ionization. A positive correlation between the high whistler activity at the ground and the negative latitudinal gradients of ionization existing in the ionosphere at low latitudes during the time of observation is found. This result explains satisfactorily the problem of how the whistlers are observed on the ground at low latitudes in the absence of suitable ducts in the ionosphere.

Simulation of whistler mode propagation for low latitude stations

“…The supporting duct requires electron density fluctuation ∼5-10% at mid and high latitudes. At very low latitudes, for the ducted propagation required electron density fluctuation is few hundred percent (Singh and Tantry, 1973;Hasegawa et al, 1978). There is no physical mechanism, which can support such a high magnitude of fluctuation.…”

Precipitation of Inner-Zone Electrons by Whistler-Mode Waves from the VLF Transmitters UMS and NWC

“…Examining the doppler shifts of waves from a VLF transmitter arriving in the topside ionosphere of the conjugate hemisphere Cerisier [19741 and Edgar [1976] found that below L -2 all satellite observations can be satisfactorily explained by nonducted propagation. Ground-based observations of low L-shell whistlers are highly dependent upon magnetic storms for the production of density gradients necessary for the proper ducting of the ray paths [Singh, 1976]. All of the observations reported by Vampola and Kuck [1978] occurred during magnetically quiet or moderately disturbed (Kp < 3) conditions under which the density structures producing whistler-mode ducts are not likely to exist.…”

Electrostatic noise bands and whistler bursts observed in DEMETER satellite at low latitude and their ground observation

“…On account of active research activities in the fields of space science and seismo-electromgnetics, the Agra station (Geomagnetic lat. 18.09 2 The generation and propagation mechanism of VLF emissions and whistlers in the low latitude ionosphere and their ground observation have been a subject of great controversy over the years (Singh, 1976;Singh et al, 1981;Singh and Hayakawa, 2001). While many workers have suggested ducted propagation for these waves in the low latitude ionosphere, others have emphasized nonducted pro-longitudinal (PL) mode of propagation (see Singh and Hayakawa, 2001 and references therein).…”