22,259 research outputs found
Dust-acoustic envelope solitons in super-thermal plasmas
The modulational instability (MI) of the dust-acoustic waves (DAWs) in an
electron-positron-ion-dust plasma (containing super-thermal electrons,
positrons and ions along with negatively charged adiabatic dust grains) is
investigated by the analysis of the nonlinear Schr\"{o}dinger equation (NLSE).
To derive the NLSE, the reductive perturbation method has been employed. Two
different parametric regions for stable and unstable DAWs are observed. The
presence of super-thermal electrons, positrons and ions significantly modifies
both the stable and unstable regions. The critical wave number (at which
modulational instability sets in) depends on the super-thermal electron,
positron, and ion, and adiabatic dust concentrations.Comment: 11 pages; 8 figure
Electrostatic rogue waves in double pair plasmas
A nonlinear Schr\"{o}dinger equation is derived to investigate the
modulational instability (MI) of ion-acoustic (IA) waves (IAWs) in a double
pair plasma system containing adiabatic positive and negative ion fluids along
with super-thermal electrons and positrons. The analytical analysis predicts
two types of modes, viz. fast () and slow () IA modes. The
possible stable and unstable parametric regions for the IAWs in presence of
external perturbation can be observed for both and . The
number density of the negative ions and positrons play a vital role in
generating the IA rogue waves (IARWs) in the modulationally unstable region.
The applications of our present work in astrophysical environments [viz.
D-region () and F-region () of the Earth's
ionosphere] as well as in laboratory plasmas [viz. pair-ion Fullerene ()] are pinpointed.Comment: 5 pages; 6 figure
Self-gravitating envelope solitons in a degenerate quantum plasma system
The existence and the basic features of ion-acoustic (IA) envelope solitons
in a self-gravitating degenerate quantum plasma system (SG-DQPS), containing
inertial non-relativistically degenerate light and heavy ion species as well as
inertialess non-relativistically degenerate positron and electron species, have
been theoretically investigated by deriving the nonlinear Schr\"{o}dinger (NLS)
equation. The NLS equation, which governs the dynamics of the IA waves, has
disclosed the modulationally stable and unstable regions for the IA waves. The
unstable region allows to generate bright envelope solitons which are
modulationaly stable. It is found that the stability and the growth rate
dependent on the plasma parameters (like, mass and number density of the plasma
species). The implications of our results in astronomical compact object (viz.
white dwarfs, neutron stars, and black holes, etc.) are briefly discussed.Comment: 6 figures,6 page
Electrostatic acoustic modes in a self-gravitating complex plasma with variable charge impurities
A linear theory of dust acoustic (DA) and dust ion-acoustic (DIA) waves in a
self-gravitating collisional dusty plasma contaminated by variable-charge
impurities is presented for a self-consistent closed system. The ion-drag force
arising from the ion orbital motion as well as momentum transfer from all the
ions and self-gravitation are taken into consideration. The physical processes,
viz., dust-charge relaxation, ionization, recombination and collisional
dissipations are also taken into account self-consistently. The generalized
dispersion relation describing the coupling of the acoustic modes with the
dust-charge relaxation mode (CRM) and damping of the waves is derived and
analyzed numerically.Comment: 13 pages, 5 figures. Physics Letters A (2005,To be published
Dust-acoustic rogue waves in four component plasmas
A theoretical investigation has been made on modulational instability (MI)
and dust-acoustic (DA) rogue waves (DARWs) in a four dusty plasma medium
containing inertial negatively charged massive heavy (light) cold (hot) dust
grains as well as super-thermal electrons and non-thermal ions. The reductive
perturbation method is used to derive the nonlinear Schr\"{o}dinger equation,
and two types of modes, namely fast and slow DA modes, have been observed. The
conditions for the MI and the formation of associated DARWs are found to be
significantly modified by the effects of non-thermality of ions (),
super-thermality of electrons (), density-ratio of non-thermal ion to
cold dust (), and mass-ratio of cold dust to hot dust (), etc.
The implications of our current investigation in space and laboratory plasmas
are briefly discussed.Comment: 5 figures; 5 page
Rogue waves in multi-pair plasma medium
The nonlinear propagation of ion-acoustic (IA) waves (IAWs), which are
governed by the nonlinear Schr\"{o}dinger equation (NLSE), in multi-pair
plasmas (MPPs) containing adiabatic positive and negative ion fluids as well as
non-extensive (-distributed) electrons and positrons, is theoretically
investigated. It is observed that the MPP under consideration supports two
types of modes (namely, fast and slow IA modes), and the modulationally stable
and unstable parametric regimes for the fast and slow IA modes are determined
by the sign of the ratio of the dispersive coefficient to the nonlinear one. It
is also found that the modulationally unstable regime generates highly
energetic IA rogue waves (IARWs), and the amplitude as well as the width of the
IARWs decrease with increase in the value of (for both and
limits). These new striking features of the IARWs are found to be applicable in
the space [viz. D-region () and F-region () of
the Earth's ionosphere] and laboratory MPPs [viz. fullerene ()].Comment: 8 figures, 5 page
Self-gravitating envelope solitons in astrophysical compact objects
The propagation of ion-acoustic waves (IAWs) in a collisionless unmagnetized
self-gravitating degenerate quantum plasma system (SG-DQPS) has been studied
theoretically for the first time. A nonlinear Schr\"{o}dinger equation is
derived by using the reductive perturbation method to study the nonlinear
dynamics of the IAWs in the SG-DQPS. It is found that for ()
(where is critical value of the propagation constant which determines
the stable and unstable region of IAWs) the IAWs are modulationally unstable
(stable), and that depends only on the ratio of the electron number
density to light ion number density. It is also observed that the
self-gravitating bright envelope solitons are modulationally stable. The
results obtained from our present investigation are useful for understanding
the nonlinear propagation of the IAWs in astrophysical compact objects like
white dwarfs and neutron stars.Comment: 6 figure
On A New Form of Darboux-B\"acklund Transformation for DNLS Equation-Mixed and Rational Type Solutions
A new form of Darboux-B\"acklund transformation and its higher order form is
derived for Derivative Nonlinear Schrodinger Equation(DNLS). The new form
arises due to the different form of Lax pair. It is observed that by a special
choice of the eigenvalue of DB transformation one can generate a mixed form of
solution(containing both algebraic and exponential dependence on (x, t) can be
generated. On the other hand by adopting a new methodology due to Neugebauer
et. al. it is found that purely rational solution can be constructed. The two
different approach yields different class of solution and are compared.Comment: 12 pages 8 figure
Solitary Optical pulse propagation in fused fibre coupler, Effect of Raman Scattering and switching
We analyse the motion of solitary type optical pulse in a fused optical fibre
coupler when inter channel raman scattering (IRS) is taken into account and
same type of dispersion management is used for both the core. The paper is
divided into two sections . In the first half we utilise a moment method to
study the variations of the different parameters of the Gaussian pulse, such as
chirp, frequency, energy etc. while in the second half assuming a general form
of the stationary pulse we discuss the switching phenomena due to the coupling.
It is shown that lauching a pulse in one arm of the coupler can generate pulses
in both the arms, but the patterns differs in a significant manner when the
strength of IRS gets changedComment: 8 pages, 8 figures. Chaos, Solitons, Fractals (2005, to appear
On The Darboux B\"acklund Transformation of Optical Solitons with Resonant and Nonresonant Nonlinearity
Solitons in nonlinear optics holds a special role both in theoretical and
experimental studies. Several types of evolution equations are seen to govern
different situation of physical relevance. One such is the existence of both
resonant and nonresonant situation in optical fibre. The corresponding
evolution equation was devised by Doktorov et. al., which consists of a forced
NLS equation along with two other equations for population difference and
polarization. Here, we have followed an earlier formulation of Neugebauer for
Darboux-B\"acklund transformation for this coupled systems. This formalism has
the advantage that one can write the N-soliton solution altogether.An important
difference with the usual non-linear system is that all the field variables are
not present in both part of Lax operator. So we are to apply the DT to both
part separately.Comment: 6 pages no figure
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