• C B Dwivedi

      Articles written in Pramana – Journal of Physics

    • Possibility of weakly charged nonlinear solitary dust clouds near the continuum threshold of dust population in a quasi-neutral dusty plasma

      S K Baishya Joyanti Chutia M K Kalita G C Das C B Dwivedi

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      Considering the Boltzmann response of the plasma ions and electrons and inertial dynamics of the charged dust grains, the possibility of very weak compressive soliton near the continuum limit of the dust population has been inferred. It is concluded that the behaviour of such coherent structures could be well described by the numerical analysis of the derived nonlinear classical energy integral equation for bounded solutions. These seem to be higher order dispersive structures within acoustic limit of the nonlinear turbulence. It is observed that the dust density enhancement beyond the continuum threshold causes regular increment in width and amplitude of the soliton structures. It is found that the soliton amplitude sensitively depends on the massive impurity’s population. These coherent structures could be visualized as weakly charged solitary dust clouds of finite extension (∼ plasma Debye length) within Boltzmann environment of plasma particles in their local surroundings. The seeding mechanism of such clouds may be attributed to some plasma instabilities driven by either internal or external free energy sources. Numerical analysis of the problem concludes that the experimental observations of such clouds could be possible in low density plasma regime. It is deduced that for plasma density ∼ 106 cm-3 at temperatures of a few electron volts and for micron to l0nm sized dust grains, the observation of such structures could be possible within wide range variability of the dust population density.

    • Stability analysis of a model equilibrium for a gravito-electrostatic sheath in a colloidal plasma under external gravity effect

      KAvita Rani Rajkhowa C B Dwivedi S Bujarbarua

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      The present contribution tries to find a scientific answer to the question of stability of an equilibrium plasma sheath in a colloidal plasma system under external gravity effect. A model equilibrium of hydrodynamical character has been discussed on the basis of quasi-hydrostatic approximation of levitational condition. It is found that such an equilibrium is highly unstable to a modified-ion acoustic wave with a conditional likelihood of linear driving of the so-called acoustic mode too. Thus, it is reported (within fluid treatment) that a plasma-sheath edge in a colloidal plasma under external gravity effect could be highly sensitive to the acoustic turbulence. Its consequential role on possible physical mechanism of Coulomb phase transition has been conjectured. However, more rigorous calculations as future course of work are required to corroborate our phenomenological suggestions.

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