Samiran Ghosh

Dust acoustic solitary wave with variable dust charge: Role of negative ions

The role of negative ions on small but finite amplitude dust acoustic solitary wave including the effects of high and low charging rates of dust grains compared to the dust oscillation frequency in electronegative dusty plasma is investigated. In the case of high charging rate, the solitary wave is governed by Korteweg–de Vries (KdV) equation, but in the case of low charging rate, it is governed by KdV equation with a linear damping term. Numerical investigations reveal that in both cases dust acoustic soliton sharpens (flatens) and soliton width decreases (increases) with the increase of negative-ion number density (temperature). Also, the negative ions reduce the damping rate.

Dust acoustic shock wave in electronegative dusty plasma: Roles of weak magnetic field

The effects of nonsteady dust charge variations and weak magnetic field on small but finite amplitude nonlinear dust acoustic wave in electronegative dusty plasma are investigated. The dynamics of the nonlinear wave are governed by a Korteweg–de Vries Burger equation that possesses dispersive shock wave. The weak magnetic field is responsible for the dispersive term, whereas nonsteady dust charge variation is responsible for dissipative term, i.e., the Burger term. The coefficient of dissipative term depends only on the obliqueness of the magnetic field. It is found that for parallel propagation the dynamics of the nonlinear wave are governed by the Burger equation that possesses monotonic shock wave. The relevances of the findings to cometary dusty plasma, e.g., Comet Halley are briefly discussed.

Effect of ionization on ion acoustic solitary waves in a collisional dusty plasma

The nonlinear wave propagation characteristics of ion acoustic (IA) solitary waves in a dusty plasma, i.e. dust ion acoustic (DIA) solitary waves in the presence of ionization. collisions of ions with dust grains and with the background neutral gas, have been investigated by employing a reductive perturbation technique. It has been found that the nonlinear DIA wave is governed by Korteweg-de Vries (KdV) equation with a positive or negative linear damping term. It has also been found that the ionization instability leads to the exponential growth of the DIA solitary wave amplitude with time. whereas ion -dust and ion neutral collisions reduce the growth rate.

Weakly dissipative ion acoustic solitary waves in a dusty plasma : roles of dust charge variation, ion loss and ionization

The nonlinear propagation characteristics of dust ion acoustic waves in the presence of weak dissipations arising due to the low rates (compared to the ion oscillation frequency) of ionization, ion loss and dust charging are investigated. It is found that the ion acoustic solitary wave in such a dusty plasma is weakly dissipative in nature and is governed by a modified form of the Korteweg-de Vries equation. The analytical solution reveals that the ionization has a destabilizing effect, whereas ion loss and dust charge variation play a stabilizing role to control the ionization instability.

Large amplitude shock wave in a strongly coupled dusty plasma due to delayed charging

The effect of delayed charging on nonlinear characteristics of a large amplitude longitudinal dust acoustic wave in the “kinetic regime” of a strongly coupled dusty plasma described by the generalized hydrodynamic equation has been investigated. Numerical investigations reveal that delayed charging induced anomalous dissipation causes the generation of a large amplitude shock wave in a strongly coupled dusty plasma only for Mach numbers lying between a minimum and a maximum value. It is found that the shock can cause the state transition from a strongly coupled to a weakly coupled state. In the case of high dust flow velocity the shock height is higher than the case of low flow velocity in comparison with the ion thermal velocity.

Reply to Comment on ‘Effect of ionization on ion acoustic solitary waves in a collisional dusty plasma’ by J. Vranjes et al.

The main objective of the Comment made by J. Vranjes et al. is that the source–sink approach in studying physical phenomena, such as the ionization instability, is suspect. Also the term

Response to “Comment on ‘Nonlinear properties of small amplitude dust ion acoustic solitary waves’” [Phys. Plasmas 15, 104703 (2008)]

(Q_{\rm i}-\nu_{\rm L} n_{\rm i})v_{\rm i}

Ion acoustic solitons and double layers in electron–positron–ion plasmas with dust particulates

in the ion momentum conservation equation of the source–sink model used by [1] is improper.

Formation of ion acoustic weak double layers in a dusty plasma

The objections are not justified. It should have been noted that ion charge number zi=1 throughout the referred paper [Ghosh et al., Phys. Plasmas 7, 3594 (2000)]. There is no inconsistency in the formulation of the referred paper as explained in the text.