An explanation of the observation of whistler-mode chorus emissions at the Indian Antarctic station, Maitri (L=4.5)

Observation of whistler-mode chorus emissions recorded at the Indian Antarctic station, Maitri (lat = 70 degrees 46'S, long = 11 degrees 50'E, L = 4(5), during a quiet period on 5 February 2001 has been reported. The detailed spectral analysis of recorded chorus emissions shows that each chorus element originates from the upper edge of the underlying hiss band. To explain the observed dynamic spectra of these chorus emissions, a possible generation mechanism is presented based on the recent nonlinear theory. It is observed that the seeds of chorus emissions with rising frequency are generated near the magnetic equator as a result of a nonlinear growth mechanism that depends on the wave amplitude. On the basis of this theory, the frequency sweep rate of chorus emission is computed and compared with that of our experimentally observed values, which in general shows good agreement.