Observation of discrete VLF emissions at low latitudes and their generation mechanism

Different type of discrete VLF emissions recorded at low-latitude ground stations Varanasi (geomag. lat., 14°55′N, geomag. long., 154°E, L = 1.07), Jammu (geomag. lat., 22°26′N, L = 1.17) and Gulmarg (geomag. lat., 24°26′N, geomag. long., 147°9′E, L = 1.28) are reported and spectral analysis of these emissions have been carried out. To explain various temporal and spectral features of these emissions, a possible generation mechanism has been presented based on the backward wave oscillator (BWO) regime of the magnetospheric cyclotron maser. On the basis of this model, we have computed various discrete emission parameters as well as some magnetospheric parameters relevant to the generation process. A comparison of the observed discrete characteristics with the proposed generation mechanism shows a good agreement with the BWO model.