[01] D. P. Nandedkar, Department of Electrical Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai, India.

In a previous paper (Nandedkar and Bhagavat 1970) [4] an analysis of damped oscillations in the plasma has been carried out. In the present paper, it is shown that the steady state amplitude of sustained electronic damped oscillations in the plasma in presence of an external d.c. electric field is greater than that in the case of the eigen-frequency damped oscillations when the applied d.c. electric field is removed. In both the cases, the steady state amplitude exists well inside the screening sphere. The amplitude being measured with respect to an ion at the center of the screening sphere. Ultimately an expression for the frequency of sustained electronic damped oscillations, in the weakly ionized plasma in presence of a low damping is developed. Further electron collision frequency term, in the low density plasma, is considered to be different in the presence and in the absence of the applied d.c. electric field. The collision frequency being smaller in the previous case, than in the later case. Moreover the distribution of electronic free paths is not neglected while determining the damping force constant part in the equation of motion of the electron in the absence of the applied d.c. electric field unlike in the case when sustained damped oscillations exist. Knowing the electron density, collision frequency and frequency of damped oscillations in the plasma in the presence of the external d.c. electric field experimentally, the values of charge to mass ratio of an electron and classical radius of a gas molecule viz., that of air are determined. In the end it is illustrated that, how the present model of weakly ionized plasma leads to the similar expression for the plasma frequency due to Tonks and Langmuir (Tonks and Langmuir 1929) [5] and to the similar expression for the complex dielectric constant of plasma basically due to Appleton and Chapman (Appleton and Chapman 1932) [6] as the limiting cases.

Damped-Oscillations, Screening-Sphere, Molecular-Radius, Electronic-Charge, Electronic-Mass

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