arXiv subjects

S. Jaiswal

Publications and source records attributed to S. Jaiswal.

22 records · Page 2Linked to original sources

arXiv2016

Experimental investigation of flow induced dust acoustic shock waves in a complex plasma

We report on experimental observations of flow induced large amplitude dust-acoustic shock waves (DASW) in a complex plasma. The experiments have been carried out in a $Π$ shaped DC glow discharge experimental device using kaolin particles as the dust component in a background of Argon plasma. A strong supersonic flow of the dust fluid is induced by adjusting the pumping speed and neutral gas flow into the device. An isolated copper wire mounted on the cathode acts as a potential barrier to the flow of dust particles. A sudden change of gas flow rate is used to trigger the onset of high velocity dust acoustic shocks whose dynamics are captured by fast video pictures of the evolving structures. The physical characteristics of these shocks are delineated through a parametric scan of their dynamical properties over a range of flow speeds and potential hill heights. The observed evolution of the shock waves and their propagation characteristics are found to compare well with model numerical results based on a modified Korteweg-de-Vries-Burgers type equation.

physics.plasm-ph↗

arXiv2016

Theoretical study of head-on collision of dust acoustic solitary waves in a strongly coupled complex plasma

We investigate the propagation characteristics of two counter propagating dust acoustic solitary waves (DASWs) undergoing a head-on collision, in the presence of strong coupling between micron sized charged dust particles in a complex plasma. A coupled set of nonlinear dynamical equations describing the evolution of the two DASWs using the extended Poincaré-Lighthill-Kuo perturbation technique is derived. The nature and extent of post collision phase-shifts of these solitary waves are studied over a wide range of dusty plasma parameters in a strongly and a weakly coupled medium. We find a significant change in the nature and amount of phase delay in the strongly coupled regime as compared to a weakly coupled regime. The phase shift is seen to change its sign beyond a threshold value of compressibility of the medium for a given set of dusty plasma parameters.

physics.plasm-ph↗

arXiv2015

Dusty Plasma Experimental (DPEx) device for complex plasma experiments with flow

A versatile table-top dusty plasma experimental (DPEx) device to study flow induced excitations of linear and nonlinear waves/structures in a complex plasma is presented. In this {$Π$}-shaped apparatus a DC glow discharge plasma is produced between a disc shaped anode and a grounded long cathode {tray} by applying a high voltage DC in the background of a neutral gas {(Argon)} and subsequently a dusty plasma is created by introducing micron sized dust particles that get charged and levitated in the sheath region. A flow of the dust particles is induced in a controlled manner by adjusting the pumping speed and the gas flow rate into the device. A full characterisation of the plasma, using Langmuir and emissive probe data, and that of the dusty plasma using particle tracking data with the help of an idl based (super) Particle Identification and Tracking (sPIT) code is reported. Experimental results on the variation of the dust flow velocity as a function of the neutral pressure and the gas flow rate are given. {The neutral drag force acting on the particles and the Epstein coefficient are estimated from the initial acceleration of the particles}. The potential experimental capabilities of the device for conducting fundamental studies of flow induced instabilities are discussed.

physics.plasm-ph↗

arXiv2013

Devasthal Fast Optical Telescope observations of Wolf-Rayet dwarf galaxy Mrk 996

The Devasthal Fast Optical Telescope (DFOT) is a 1.3 meter aperture optical telescope, recently installed at Devasthal, Nainital. We present here the first results using an \Ha filter with this telescope on a Wolf-Rayet dwarf galaxy Mrk 996. The instrumental response and the \Ha sensitivity obtained with the telescope are $(3.3 \pm 0.3)\times 10^{-15} (erg s^{-1} cm^{-2})/(counts s^{-1})$ and $7.5\times10^{-17} erg s^{-1} cm^{-2} arcsec^{-2}$ respectively. The \Ha flux and the equivalent width for Mrk~996 are estimated as $(132 \pm 37)\times 10^{-14} erg s^{-1} cm^{-2}$ and $\sim$96 $\mathring{A}$ respectively. The star formation rate is estimated as $0.4\pm0.1 M_\odot$yr$^{-1}$. Mrk~996 deviates from the radio-FIR correlation known for normal star forming galaxies with a deficiency in its radio continuum. The ionized gas as traced by \Ha emission is found in a disk shape which is misaligned with respect to the old stellar disk. This misalignment is indicative of a recent tidal interaction in the galaxy. We believe that galaxy-galaxy tidal interaction is the main cause of the WR phase in Mrk~996.

astro-ph.CO↗