RADIO-EMISSION OF PSR J0437-4715 AT 327 MHZ

More than 412,000 single pulses from the brightest millisecond radio p ulsar PSR J0437-4715 were obtained at 327 MHz using the Ooty Radio Tel escope. This pulsar displays neither the nulling nor the systematic dr ifting phenomenon found in several normal (long period) pulsars. A rig orous upper limit to the percentage of nulling in PSR J0437-4715 is 0. 0016%. However, its integrated profile varies on timescales ranging fr om approximate to 500 periods to days; the variation is slow and unlik e the mode-changing phenomenon of normal pulsars. About 3% of the inte nsity of PSR J0437-4715 varies quasi-periodically, particularly at ear ly pulse phases within the integrated profile. Its fluctuation spectru m has a weak feature at the mean value of 0.253 +/- 0.002 cycles per p eriod, with an average rms width of 0.067 +/- 0.005 cycles per period, but both parameters vary from phase to phase within the integrated pr ofile, which has not been noticed so far in pulsars. Our results are i mportant to resolve the issue whether the radio emission of millisecon d pulsars is similar to that of normal pulsars.