• Tarsem Singh

      Articles written in Pramana – Journal of Physics

    • Dynamics of self-focusing and self-phase modulation of elliptic Gaussian laser beam in a Kerr-medium

      Tarsem Singh Nareshpal Singh Saini Shyam Sunder Kaul

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      Using a direct variational technique involving elliptic Gaussian laser beam trial function, the combined effect of non-linearity and diffraction on wave propagation of optical beam in a homogeneous bulk Kerr-medium is presented. Particular emphasis is put on the variation of beam width and longitudinal phase delay with the distance of propagation. It is observed that no stationary self-trapping is possible. The regularized phase is also seen to be always negative.

    • Effect of rippled laser beam on excitation of ion acoustic wave

      Nareshpal Singh Saini Tarsem Singh Gill

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      Growth of a radially symmetrical ripple, superimposed on a Gaussian laser beam in collisional unmagnetised plasma is investigated. From numerical computation, it is observed that self-focusing of main beam as well as ripple determine the growth dynamics of ripple with the distance of propagation. The effect of growing ripple on excitation of ion acoustic wave (IAW) has also been studied.

    • Optical guiding of laser beam in nonuniform plasma

      Tarsem Singh Gill

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      A plasma channel produced by a short ionising laser pulse is axially nonuniform resulting from the self-defocusing. Through such preformed plasma channel, when a delayed pulse propagates, the phenomena of diffraction, refraction and self-phase modulation come into play. We have solved the nonlinear parabolic partial differential equation governing the propagation characteristics for an approximate analytical solution using variational approach. Results are compared with the theoretical model of Liu and Tripathi (Phys. Plasmas1, 3100 (1994)) based on paraxial ray approximation. Particular emphasis is on both beam width and longitudinal phase delay which are crucial to many applications.

    • Effect of nonthermal ion distribution and dust temperature on nonlinear dust acoustic solitary waves

      Tarsem Singh Gill Harvinder Kaur

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      The effects of nonthermal ion distribution and finite dust temperature are incorporated in the investigation of nonlinear dust acoustic waves in an unmagnetized dusty plasma. Sagdeev pseudopotential method which takes into account the full nonlinearity of plasma equations, is used here to study solitary wave solutions. Possibility of co-existence of refractive and compressive solitons as a function of Mach number, dust temperature and concentration of nonthermal ions, is considered. For the fixed value of nonthermal ions, it is found that the effect of increase in dust temperature is to reduce the range of co-existence of compressive and refractive solitons. Particular concentration of nonthermal ions results in disappearance of refractive solitons while the decrease in dust temperature, at this concentration restores the lost refractive solitons.

    • Ion-acoustic solitons in multispecies spatially inhomogeneous plasmas

      Tarsem Singh Gill Harvinder Kaur Nareshpal Singh Saini

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      Ion-acoustic solitons are investigated in the spatially inhomogeneous plasma having electrons-positrons and ions. The soliton characteristics are described by Korteweg-de Vries equation which has an additional term. The density and temperature of different species play an important role for the amplitude and width of the solitons. Numerical calculations show only the possibility of compressive solitons. Further, analytical results predict that the peak amplitude of soliton decreases with the decrease of density gradient. Soliton characteristics like peak amplitude and width are substantially different from those based on KdV theory for homogeneous plasmas

    • Propagation characteristics of ion-acoustic double layer in multicomponent inhomogeneous auroral zone plasma


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      In the present investigation, ion-acoustic double layers in an inhomogeneous plasma consisting of Maxwellian and non-thermal distributions of electrons are studied.We have derived a modified Korteweg–de Vries (mKdV) equation for ion-acoustic double layers propagating in a collisionless inhomogeneous plasma. It is observed that the non-thermal parameters affect the amplitude and width of the double layer which further depend on the density.

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