%0 Journal Article
%T Negatively Charged Oxygen Ions as a Plasma Diagnostic Tool: Application to Comets
%A Sreekala Gopinathan
%A Sijo Sebastian
%A Noble Abraham
%A Savithri Devi
%A Venugopal Chandu
%A Renuka Gangadharan
%J Open Access Library Journal
%V 1
%N 4
%P 1-9
%@ 2333-9721
%D 2014
%I Open Access Library
%R 10.4236/oalib.1100570
%X We study the stability of the ion-acoustic (IA) wave in a collisional plasma composed of hydrogen, positively and negatively charged oxygen ions, electrons and neutral atoms. This composition approximates very well the plasma environment around a comet. A solution of the dispersion relation yields a frequency for the IA wave at around the hydrogen plasma frequency. The growth/ damping rate is sensitively dependent on the ring parameters <sup><i>u</i></sup><sub><i>¡Ís</i></sub> (the ring speed) and <sup><i>v</i></sup> <sub><i>ts</i></sub> (the thermal spread). The growth rate of the wave, which decreases with increasing collisional frequencies, is larger when <sup><i>u</i></sup><sub><i>¡Ís&nbsp;</i></sub>£¼&nbsp;<sup><i>v</i></sup> <sub><i>ts&nbsp;</i></sub>. In the presence of negatively charged oxygen ions, the phase and group velocities of the IA wave behave in a contrasting manner when <sup><i>u</i></sup><sub><i>¡Ís&nbsp;</i></sub>£¼&nbsp;<sup><i>v</i></sup> <sub><i>ts</i></sub> (and viceversa). We propose that this behaviour be exploited as a diagnostic tool for the detection of these ions and also their thermalization.
%K Ion-Acoustic Wave
%K Negative Ions
%K Diagnostic Tool
%K Cometary Plasma
%U http://www.oalib.com/paper/3064435