Magnetospheric discrete vlf rising-tone chorus emissions observed at indian antarctic station maitri (l = 4.5), antarctica

The magnetospheric discrete VLF chorus emissions observed at Indian Antarctic Station Maitri, Antarctica (geomag. lat. = 700 46/ S, geomag. log. = 110 50/ E, L = 4.5) has been analyzed during quite period on 5th February 2001 are presented. The detailed spectral analysis of recorded discrete VLF chorus emissions, we found that intensity seems to decrease with increase in frequency and also it varies from event to event and each chorus emissions originates from upper edge of narrow hiss band and chorus events are hiss-triggered. They are generated in the magnetosphere near the geomagnetic equator by trapping of the energetic electrons. To explain the observed dynamic spectra of these events, a possible generation mechanism is presented based on the Helliwell’s theory. To understand the generation mechanism of discrete VLF chorus emissions, using Helliwell’s (1967) theory and previous presented satellite VLF data, some plasmaspheric parameters such as phase velocity, group velocity, parallel and perpendicular velocity of interacting electrons, source length, source location, wave magnetic field, power density, transverse current etc. are computed. Our results are good agreement to other workers.