Alfven Wave Instabilities Related with Excess Charge as a Source of Jovian Magnetospheric Micropulsations

Hydromagnetic wave instabilities (Alfven wave instabilities, the physical picture of this instability is given in terms of wave-wave interaction) excited by an electron or ion beam passing through IO tours in the Jovian magnetosphere has been studied in the case of low wave frequency and small wave number in the presence of excess charge in the media. It has been obtained that the excess charge near IO has the dominant role in modifying the Alfvan wave instabilities in comparison to the other parameters. The central frequency of this instability is lying within the range of micropulsations for the presence of excess charge of 10-3 times the ambient plasma in the Jovian magnetosphere. Hence this excited Alfvan wave instabilities is the one of the possible generation mechanism for the micro-pulsations recorded by Voyager 1 and 2 in the Jovian Magnetosphere.