Experimental evidence of ion plasma oscillations in the apogee region of the Nike-Apache rocket

Several Nike-Apache rockets with Lang muir probe payloads were launched from Thumba (India) to study the disturbances produced by a moving rocket. The rockets were launched during different times of the day and night. It was found that low frequency ion plasma oscillations of the order of 1 KHz frequency were observed in the altitude region 145 to 200 km. This altitude region corresponds to the rocket apogee region where the rocket velocity is subsonic. The amplitude of the fluctuations was about 1 to 2% and was found to be dependant on rocket velocity electron density in the ambient medium, rocket spin and probe voltage. It was noticed that in the case of Centaure and Petrel rockets such types of oscillations were not observed. The Nike-Apache rockets are made of aluminium while Centaure and Petrel rockets are made of stainless steel.