arXiv subjects

A. P. Misra

Publications and source records attributed to A. P. Misra.

At least 37 records · Page 2Linked to original sources

arXiv2023

Chaos and complexity in the dynamics of nonlinear Alfvén waves in a magnetoplasma

The nonlinear dynamics of circularly polarized dispersive Alfv{é}n wave (AW) envelopes coupled to the driven ion sound waves of plasma slow response is studied in a uniform magnetoplasma. By restricting the wave dynamics to a few number of harmonic modes, a low-dimensional dynamical model is proposed to describe the nonlinear wave-wave interactions. It is found that two subintervals of the wave number of modulation $k$ of AW envelope exists, namely $(3/4)k_c<k<k_c$ and $0<k<(3/4)k_c$, where $k_c$ is the critical value of $k$ below which the modulational instability (MI) occurs. In the former, where the MI growth rate is low, the periodic and/or quasi-periodic states are shown to occur, whereas the latter, where the MI growth is high, brings about the chaotic states. The existence of these states is established by the analyses of Lyapunov exponent spectra together with the bifurcation diagram and phase-space portraits of dynamical variables. Furthermore, the complexities of chaotic phase spaces in the nonlinear motion are measured by the estimations of the correlation dimension (CD) as well as the approximate entropy (ApEn), and compared with those for the known H{é}non map and the Lorenz system in which a good qualitative agreement is noted. The chaotic motion thus predicted in a low-dimensional model can be a prerequisite for the onset of Alfv{é}nic wave turbulence to be observed in a higher dimensional model that and is relevant in the Earth's ionosphere and magnetosphere.

physics.plasm-ph↗

arXiv2022

Magnetohydrodynamic instabilities in a self-gravitating rotating cosmic plasma

The generation of magnetohydrodynamic (MHD) waves and their instabilities are studied in galactic gaseous rotating plasmas with the effects of the magnetic field, the self gravity, the diffusion-convection of cosmic rays as well as the gas and cosmic-ray pressures. The coupling of the Jeans, Alfv{é}n and magnetosonic waves, and the conditions of damping or instability are studied in three different cases, namely when the propagation direction is perpendicular, parallel and oblique to the static magnetic field, and are shown to be significantly modified by the effects of the Coriolis force due to the rotation of cosmic fluids and the cosmic-ray diffusion. The coupled modes can be damped or anti-damped depending on the wave number is above or below the Jeans critical wave number that is reduced by the effects of the Coriolis force and the cosmic-ray pressure. It is found that the deviation of the axis of rotation from the direction of the static magnetic field gives rise to the coupling between the Alfv{é}n wave and the classical Jeans mode which otherwise results into the modified slow and fast Alfv{é}n waves as well as the modified classical Jeans modes. Furthermore, due to the effects of the cosmic rays diffusion, there appears a new wave mode (may be called the fast Jeans mode) in the intermediate frequency regimes of the slow and fast Alfv{é}n waves, which seems to be dispersionless in the long-wavelength propagation and has a lower growth rate of instability in the high density regimes of galaxies. The dispersion properties and the instabilities of different kinds of MHD waves reported here can play pivotal roles in the formation of various galactic structures at different length scales.

physics.plasm-ph↗

arXiv2022

Drift ion-acoustic waves in a nonuniform rotating magnetoplasma with two-temperature superthermal electrons

The theory of low-frequency (in comparison with the ion cyclotron frequency), long wavelength, electrostatic drift ion-acoustic waves (IAWs) is studied in a nonuniform rotating magnetoplasma with two temperature superthermal electrons. In the linear limit, the coupling of IAWs and drift waves by the density inhomogeneity is shown to produce a new wave mode which typically depends on the density gradient, the rotational frequency and the spectral indexes of superthermal electrons. In the nonlinear regime, an evolution equation for the drift IAWs is derived by the dispersion approach, and using the Jacobi elliptic function expansion technique its exact solitary and periodic wave solutions (namely, cnoidal and dnoidal) are also obtained. The properties of these solutions are numerically examined and it is found that they are significantly modified by the effects of the background density gradient, the superthermality of electrons and the Coriolis force associated with the rotational motion of ions.

physics.plasm-ph↗

arXiv2022

Nonlinear evolution of internal gravity waves in the Earth's ionosphere: Analytical and numerical approach

The nonlinear propagation of internal gravity waves in the weakly ionized, incompressible Earth's ionosphere is studied using the fluid theory approach. Previous theory in the literature is advanced by the effects of the terrestrial inhomogeneous magnetic field embedded in weakly ionized ionospheric layers ranging in altitude from about $50$ to $500$ km. It is shown that the ionospheric conducting fluids can support the formation of solitary dipolar vortices (or modons). Both analytical and numerical solutions of the latter are obtained and analyzed. It is found that in absence of the Pedersen conductivity, different vortex structures with different space localization can be formed which can move with the supersonic velocity without any energy loss. However, its presence can cause the amplitude of the solitary vortices to decay with time and the vortex structure can completely disappear owing to the energy loss. Such energy loss can be delayed, i.e., the vortex structure can prevail for relatively a longer time if the nonlinear effects associated with either the stream function or the density variation become significantly higher than the dissipation due to the Pedersen conductivity. The main characteristic dynamic parameters are also defined which are in good correlation with the existing experimental data.

physics.ao-ph↗

arXiv2022

Internal Gravity Waves in the Earth's Ionosphere

The theory of low-frequency internal gravity waves (IGWs) is readdressed in the stable stratified weakly ionized Earth's ionosphere. The formation of dipolar vortex structures and their dynamical evolution, as well as, the emergence of chaos in the wave-wave interactions are studied both in presence and absence of the Pedersen conductivity. The latter is shown to inhibit the formation of solitary vortices and the onset of chaos.

physics.ao-ph↗

arXiv2021

Effects of Coriolis force on the nonlinear interactions of acoustic-gravity waves in the atmosphere

The nonlinear theory of acoustic-gravity waves (AGWs) in the atmosphere is revisited with the effects of the Coriolis force. Previous theory in the literature [Phys. Scr. \textbf{90} (2015) 055001] is advanced. Starting from a set of fluid equations modified by the Coriolis force, a general linear dispersion relation is derived which manifests the coupling of the high-frequency acoustic-gravity waves (AGWs) and the low-frequency internal gravity waves (IGWs). The frequency of IGWs is enhanced by the Earth's angular velocity. The latter also significantly modifies the nonlinear coupling of AGWs and IGWs whose evolutions are described by the Zakharov approach as well as the Wigner-Moyal formalism. The consequences of AGWs and the two equivalent evolution equations modified by the Coriolis force are briefly discussed.

physics.ao-ph↗

arXiv2020

Stability and evolution of electromagnetic solitons in relativistic degenerate laser plasmas

The dynamical behaviors of electromagnetic (EM) solitons formed due to nonlinear interaction of linearly polarized intense laser light and relativistic degenerate plasmas are studied. In the slow motion approximation of relativistic dynamics, the evolution of weakly nonlinear EM envelope is described by the generalized nonlinear Schr{ö}dinger (GNLS) equation with local and nonlocal nonlinearities. Using the Vakhitov-Kolokolov criteria, the stability of an EM soliton solution of the GNLS equation is studied. Different stable and unstable regions are demonstrated with the effects of soliton velocity, soliton eigenfrequency, as well as the degeneracy parameter $R=p_{Fe}/m_ec$, where $p_{Fe}$ is the Fermi momentum and $m_e$ the electron mass, and $c$ is the speed of light in vacuum. It is found that the stability region shifts to an unstable one and is significantly reduced as one enters from the regimes of weakly relativistic $(R\ll1)$ to ultrarelativistic $(R\gg1)$ degeneracy of electrons. The analytically predicted results are in good agreement with the simulation results of the GNLS equation. It is shown that the standing EM soliton solutions are stable. However, the moving solitons can be stable or unstable depending on the values of soliton velocity, the eigenfrequency or the degeneracy parameter. The latter with strong degeneracy $(R>1)$ can eventually lead to soliton collapse.

physics.plasm-ph↗

arXiv2020

Optical surface plasmons at a metal-crystal interface with the Drude-Lorentz model for material permittivity

The theory of surface electromagnetic waves (SEMWs) propagating at optical frequencies along the interface of an isotropic noble metal [e.g., gold (Au)] and a uniaxial crystal [e.g., Rutile (TiO$_2$)] is revisited with the Drude-Lorentz (DL) model for the complex dielectric material permittivity $(ε_p)$. The latter accounts for the contributions of both the \textit{intraband} transitions of the free electrons and the multiple \textit{interband} transitions of the bound electrons in metals. The propagation characteristics of the wave vectors and wave frequency of SEMWs, the hybridization factors, i.e., the amplitude ratios between the transverse-electric (TE) and transverse-magnetic (TM) modes in the isotropic metal, and between the ordinary and extraordinary modes in the uniaxial substrate are studied numerically. It is found that the results are significantly modified from those with the Drude model for $ε_p$, especially in the short-wavelength spectra ($λ\lesssim500$ nm) and with a small deviation of the orientation of the optical axis. The excitation of such SEMWs can have novel applications in transportation of EM signals in a specified direction at optical frequencies ($\sim $ PHz).

physics.app-ph↗

arXiv2020

Large amplitude electromagnetic solitons in a fully relativistic magnetized electron-positron-pair plasma

Nonlinear propagation of purely stationary large amplitude electromagnetic (EM) solitary waves in a magnetized electron-positron (EP) plasma is studied using a fully relativistic two-fluid hydrodynamic model which accounts for physical regimes of both weakly relativistic $(P\ll nmc^2)$ and ultrarelativistic $(P\gg nmc^2)$ random thermal energies. Here, $P$ is the thermal pressure, $n$ the number density and $m$ the mass of a particle, and $c$ is the speed of light in vacuum. Previous theory in the literature [Phys. Plasmas \textbf{11}, 3078 (2004)] is advanced and generalized by the relativistic thermal motion of both electrons and positrons. While both the sub-Alfv{é}nic and super-Alfv{é}nic solitons coexist in the weakly relativistic regime, the ultrarelativistic EP plasmas in contrast support only the sub-Alfv{é}nic solitons. Different limits of the Mach numbers and soliton amplitudes are also examined in these two physical regimes.

physics.plasm-ph↗

arXiv2020

Synchronization in networks of coupled hyperchaotic CO$_2$ lasers

A non-autonomous dynamical system is proposed to study the synchronization in networks of mutually coupled optically modulated hyperchaotic CO$_2$ lasers. By the method of master stability function (MSF) it is shown that the stable synchronous state can be reached for both the ring of diffusively coupled (RDC) and star-coupled (SC) networks of at most $24$ nodes or oscillators. A numerical simulation of the coupled $24$ hyperchaotic CO$_2$ lasers is also performed to show that the corresponding synchronization error $\lesssim10^{-6}$. Furthermore, the chimera states of the networks are found to coexist in some intervals of time and the coupling strengths where the networks are not synchronized, implying that the synchronization occurs only in some specific ranges of values of the coupling strengths.

nlin.AO↗

arXiv2020

Generation of wakefields and electromagnetic solitons in relativistic degenerate plasmas

The nonlinear interaction of intense linearly polarized electromagnetic waves (EMWs) with longitudinal electron density perturbations is revisited in relativistic degenerate plasmas. The nonlinear dynamics of the EMWs and the longitudinal field, driven by the EMW ponderomotive force, is governed by a coupled set of nonlinear partial differential equations. A numerical simulation of these coupled equations reveals that the generation of wakefields is possible in weakly relativistic degenerate plasmas with $R_0\equiv p_F/mc\ll1$ and $v_g/c\sim1$, where $p_F$ is the Fermi momentum, $m$ is the mass of electrons, $c$ is the speed of light in vacuum, and $v_g$ is the EMW group velocity. However, when the ratio $v_g/c$ is reduced to $\sim0.1$, the wakefield generation is suppressed, instead the longitudinal fields get localized to form soliton-like structures. On the other hand, in the regimes of moderate $(R_0\lesssim1)$ or strong relativistic degeneracy $(R_0>1)$ with $v_g/c\sim0.1$, only the EM solitons can be formed.

physics.plasm-ph↗

arXiv2019

Degenerating the butterfly attractor in a plasma perturbation model using nonlinear controllers

In this work, the dynamical behaviors of a low-dimensional model, which governs the interplay between a driver associated with pressure gradient and relaxation of instability due to magnetic field perturbations, are investigated. Besides that, two nonlinear controllers are constructed precisely to shift the equilibria of the plasma model apart from each other. Simulation results show that shifting the equilibria can change the spacing of chaotic attractors, and subsequently break the butterfly wings into one or two symmetric pair of coexisting chaotic attractors. Furthermore, stretching the equilibria of the system apart enough from each other gives rise to degenerate the butterfly wings into several periodic orbits. In addition, with appropriate initial conditions, the complex multistability behaviors including the coexistence of butterfly chaotic attractor with two point attractors, the coexistence of transient transition chaos with completely quasi-periodic behavior, and the coexistence of symmetric Hopf bifurcations are also observed.

nlin.CD↗

arXiv2019

Dynamical properties of acoustic-gravity waves in the atmosphere

We study the dynamical behaviors of a system of five coupled nonlinear equations that describes the dynamics of acoustic-gravity waves in the atmosphere. A linear stability analysis together with the analysis of Lyapunov exponents spectra are performed to show that the system can develop from ordered structures to chaotic states. Numerical simulation of the system of equations reveals that an interplay between the order and chaos indeed exists depending on whether the control parameter $s_1$, associated with the density scale height of acoustic-gravity waves, is below or above its critical value.

nlin.CD↗

arXiv2018

Discrete model for cloud computing: Analysis of data security and data loss

Cloud computing is recognized as one of the most promising solutions to information technology, e.g., for storing and sharing data in the web service which is sustained by a company or third party instead of storing data in a hard drive or other devices. It is essentially a physical storage system which provides large storage of data and faster computing to users over the Internet. In this cloud system, the third party allows to preserve data of clients or users only for business purpose and also for a limited period of time. The users are used to share data confidentially among themselves and to store data virtually to save the cost of physical devices as well as the time. In this paper, we propose a discrete dynamical system for cloud computing and data management of the storage service between a third party and users. A framework, comprised of different techniques and procedures for distribution of storage and their implementation with users and the third party is given. For illustration purpose, the model is considered for two users and a third party, and its dynamical properties are briefly analyzed and discussed. It is shown that the discrete system exhibits periodic, quasiperiodic and chaotic states. The latter discerns that the cloud computing system with distribution of data and storage between users and the third party may be secured. Some issues of data security are discussed and a random replication scheme is proposed to ensure that the data loss can be highly reduced compared to the existing schemes in the literature.

cs.DC↗

arXiv2018

Chaos-based image encryption using vertical-cavity surface-emitting lasers

We study the encryption and decryption processes of color images using the synchronization of polarization dynamics in a free-running vertical-cavity surface-emitting laser (VCSEL). Here, we consider a bidirectional master-slave configuration or two-way coupling with two VCSELs. The latter are shown to exhibit hyperchaos and synchronization with a high level of similarity between their emission characteristics. The coupled VCSELs are then used as a transmitter and a receiver for the communication of image or data. Furthermore, we propose a modified chaos-based image encryption algorithm using the pixel- and bit-level permutations which provides robust, faster and simpler encryption/decryption compared to many other chaos-based cryptosystems. The performances of the new cryptosystem are analyzed and compared with a recently developed scheme [Opt. Las. Eng. 90 (2017) 238-246]. The security analysis and some statistical investigations show that the proposed cryptosystem is resistant to various types of attacks and is efficient for secure communications in nonlinear optical media.

physics.optics↗

arXiv2018

Stimulated scattering instability in a relativistic plasma

We study the stimulated scattering instabilities of an intense linearly polarized electromagnetic wave (EMW) in a relativistic plasma with degenerate electrons. Starting from a relativistic hydrodynamic model and the Maxwell's equations, we derive coupled nonlinear equations for low-frequency electron and ion plasma oscillations that are driven by the EMW's ponderomotive force. The nonlinear dispersion relations are then obtained from the coupled nonlinear equations which reveal stimulated Raman scattering (SRS), stimulated Brillouin scattering (SBS), and modulational instabilities (MIs) of EMWs. It is shown that the thermal pressure of ions and the relativistic degenerate pressure of electrons significantly modify the characteristics of SRS, SBS, and MIs.

physics.plasm-ph↗

arXiv2018

Surface plasmons in a semi-bounded massless Dirac plasma

The collective excitation of surface plasmons in a massless Dirac plasma (e.g., graphene) half-space (bounded by air) is investigated using a relativistic quantum fluid model. The unique features of such surface waves are discussed and compared with those in a Fermi plasma. It is found that in contrast to Fermi plasmas, the long-wavelength surface plasmon frequency $(ω)$ in massless Dirac plasmas is explicitly nonclassical, i.e., $ω\propto1/\sqrt{\hbar}$, where $h=2π\hbar$ is the Planck's constant. Besides some apparent similarities between the surface plasmon frequencies in massless Dirac plasmas and Fermi plasmas, several notable differences are also found and discussed. Our findings elucidate the properties of surface plasmons that may propagate in degenerate plasmas where the relativistic and quantum effects play a vital role.

physics.plasm-ph↗

arXiv2018

Modulation of kinetic Alfvén waves in an intermediate low-beta magnetoplasma

We study the amplitude modulation of nonlinear kinetic Alfv{é}n waves (KAWs) in an intermediate low-beta magnetoplasma. Starting from a set of fluid equations coupled to the Maxwell's equations, we derive a coupled set of nonlinear partial differential equations (PDEs) which govern the evolution of KAW envelopes in the plasma. The modulational instability (MI) of such KAW envelopes is then studied by a nonlinear Schr{ö}dinger (NLS) equation derived from the coupled PDEs. It is shown that the KAWs can evolve into bright envelope solitons, or can undergo damping depending on whether the characteristic ratio $(α)$ of the Alfv{é}n to ion-acoustic (IA) speeds remains above or below a critical value. The parameter $α$ is also found to shift the MI domains around the $k_xk_z$ plane, where $k_x~(k_z)$ is the KAW number perpendicular (parallel) to the external magnetic field. The growth rate of MI, as well as the frequency shift and the energy transfer rate, are obtained and analyzed. The results can be useful for understanding the existence and formation of bright and dark envelope solitons, or damping of KAW envelopes in space plasmas, e.g., interplanetary space, solar winds etc.

physics.plasm-ph↗