Whistler-mode chorus emissions observed at Nanital (L= 1.16)

Observations of whistler-mode chorus emissions recorded at Nanital (190 02/ N, 14.9o 45/ E, L = 1.16) between 2200 and 0315 hours IST on 13 May and 8 June 1970 has been reported. The detailed spectral analysis of recorded chorus emissions shows that the chorus element originates from upper edge of the hiss band. To explain the observed dynamic spectra of these chorus emissions, a possible generation mechanism is presented on the non linear 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.