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Pralay Kumar Karmakar

Publications and source records attributed to Pralay Kumar Karmakar.

15 recordsLinked to original sources

Joule-Thomson Effect and Geodesic Structure of Charged AdS Black Holes in f(R,T) Coupled with Nonlinear Electrodynamics

We herein study both the Joule-Thomson (JT) expansion process and the geodesic properties of a charged anti-de Sitter (AdS) black hole arising in modified gravity with nonlinear electrodynamic (NLED) sources. Our thermodynamic study reveals that the black hole charge has the most pronounced impact on the JT behaviour. The nonlinear electromagnetic sector together with the modified gravity parameters introduces further corrections to the inversion temperature and the associated cooling characteristics. At astrophysically relevant distances, the geometry closely reproduces expected outcomes.

gr-qc

Stability and wave dynamics in polytropic Eddington-inspired Born-Infeld gravitating solar plasmas

We investigate the influence of nonlinear gravity corrections, arising from the Eddington-inspired Born-Infeld (EiBI) theory on wave dynamics, stability, and energy transport processes in polytropic, viscous, and turbulent solar plasmas. Analytical and numerical analyses of the Jeans-normalized quadratic dispersion relation demonstrate that both the EiBI gravity parameter $(χ)$ and the relative polytropic sound speed $(β)$ independently regulate oscillation frequencies, growth rates, phase velocities, perturbation energy partitioning, and outward acoustic energy flux. Positive $χ$ systematically elevates oscillation frequencies, phase velocities, and outward energy flux level by $\sim$10% relative to the Newtonian predictions, while larger $β$ enhances them by up to 55%, thereby promoting wave propagation and efficient acoustic transport. Conversely, negative $χ$ strengthens gravitational binding and increases damping rates by $\sim$40%, particularly for the \textit{g}-modes. Energy partitioning analyses reveal that the EiBI corrections fundamentally restructure the kinetic-electrostatic-gravitational energy balance. While the Newtonian gravity contributes negligibly ($<$4%), nonzero $χ$ channels up to one-third of oscillation energy into gravitational modes. The modal surface flux calculations further confirm that only the \textit{p}-modes drive outward energy transport (amplification for $χ>0$, suppression for $χ<0$). A direct comparative analysis with four years of SDO/HMI Doppler velocity observations demonstrate a robust theoretical agreement for $χ=3\times10^7$ m$^5$kg$^{-1}$s$^{-2}$, providing the first empirical constraint on the solar EiBI gravity through helioseismology. The findings offer a rigorous framework for advancing our understanding about solar plasma stability, helioseismic signatures, and ambient atmospheric energy transport processes.

astro-ph.SR

Impact of Thermodynamic Corrections on the Stability of Hayward-Anti de Sitter Black Hole Surrounded by a Fluid of Strings

We explore the modified thermodynamics of a Hayward-Anti de Sitter (H-AdS) black hole in atypical conditions, incorporating a string fluid, Hayward regularisation, and quantum entropy corrections. Our analysis reveals a first-order phase transition between small and large black hole phases, characterised by a swallowtail behaviour in the Gibbs free energy profiles. It is found that the key parameters - string fluid strength, Hayward regularisation scale, and quantum correction coefficients significantly influence the critical temperature and phase stability of the H-AdS system. It is further noticed that a large black hole phase is stabilised by these modifications, with quantum corrections smoothing the transition. This model offers a valuable framework to study quantum gravity effects on black hole thermodynamics with potential implications in analysing black hole evolution and astrophysical observations.

gr-qc

Plasma sheath physics: A circuital description, amelioration, and application

A synoptic review of the electrical circuital model-based analysis of laboratory plasma sheaths, alongside their stability features in a realistic broader horizon, is systematically presented herein. It explains the basic physics responsible for the inductive (L_sh), capacitive (C_sh), and resistive (R_sh) properties simultaneously, exhibited by plasma sheaths. The analyzed model sheath behaviors are judiciously described in the light of the state-of-the-art sheath scenarios, illustratively. The sheath-based circuital components are minutely contrasted with the traditionally available circuital counterparts. The applications of the novel circuital sheath model in widespread fields of research having both fundamental and applied importance are discussed. The main merits of modelling plasma sheaths through the circuital formalism over the existing non-circuital theoretical ones are briefly outlined, jointly with future applied scope.

physics.plasm-ph

An electric circuital analysis of laboratory plasma sheath fluctuations and propagations

The effective inductive (L), capacitive (C), and resistive (R) behavior of a plasma sheath in a conjoint coupled form is well familiar among plasma physics communities. A dynamic sheath instability in laboratory plasmas is systematically modelled herein as an electrical series-resonance LCR circuit of the above kind. It theoretically yields experimentally observed findings on coexistent plasma sheath oscillation, electric current perturbation, and subsequent plasma sheath waves (PSWs). The plasma current in the LCR circuit formalism is allowed to undergo linear (small-scale) spatiotemporal perturbations about its homogeneous equilibrium state. The oscillating sheath triggers ion-acoustic wave excitation in the bulk plasma through sheath-induced energy transfer processes. The obtained results could be applicable mainly in understanding electromagnetic communication antennas, ion energy modulation processes, diverse plasma probe diagnostics, etc.

physics.plasm-ph

Plasma fireball sheath dynamics: A brief review and meta-analysis

We present a comprehensive overview of the formation mechanism of plasma fireball sheath (PFS) structures, sheath-induced collective phenomena, associated relevant instabilities, and corresponding onset conditions. It includes an optimum set of self-illustrative schematic figures, relevantly manifesting the instability triggering dynamics, various involved metastable stages, and parametric threshold conditions. The possible damping mechanisms of excited instabilities in the usual PFS systems are also highlighted. An up-to-date experimental glimpse of both the regular fireball (RFB) and inverted fireball (IFB) classes is specifically presented. We explicitly offer illustrative appendices showing the main distinctions between (a) RFB and IFB, (b) laboratory and astrocosmic fireballs, and (c) RFB sheath and IFB sheath formations. It provides a panoptic glimpse of the current RFB and IFB studies with a special mention to both laboratory and astrospace plasmas. A holistic outline on the chronological development of the PFS research investigations, since the inception of plasma-electrode coupling studies, is outlined. A clear indication of the future fireball scope in both theoretic and applied perspectives is finally emphasized.

physics.plasm-ph

Effect of kappa-modified polarization force on Jeans instability in nonthermal EiBI-gravitating dust clouds

A semi-analytic model is developed to study the effects of kappa-distributed lighter constituents and the associated kappa-modified polarization force on the classical Jeans instability in dust molecular clouds (DMCs). The constitutive electrons and ions are considered to follow a nonthermal kappa-velocity distribution law, while the constitutive massive dust grains are treated as the EiBI-gravitating fluids. A linearized quadratic dispersion relation is derived using spherical normal mode analysis. The resulting dispersion relation and its corresponding modified instability criteria are analyzed in the hydrodynamic and kinetic regimes. The oscillatory and propagating mode characteristics are illustratively analyzed. It is seen that the EiBI gravity introduces a new velocity term in the dispersion relation. In contrast, the nonthermal kappa-distributed constituents significantly enhance the polarization force against their respective Maxwellian counterparts. The kappa-modified polarization force and the negative EiBI gravity parameter have destabilizing influences, unlike the positive EiBI parameter. An enhanced polarization interaction parameter and a positive EiBI parameter reduce the real normalized frequency. Consequently, the phase velocity exhibits strong dispersion, increasing with wavenumber until reaching saturation, after which it transitions into a weakly dispersive regime. These findings provide new insights into the formation of smaller astrophysical structures via the non-local Jeans instability in the ultracompact HII regions of dense DMCs.

astro-ph.GA

Solar GES-structure modified with EiBI gravity

In the post-Newtonian era, the Eddington-inspired Born-Infeld (EiBI) theory, considered as an improved modification of the Einsteinian general relativity formalism in the weak field regime (non-relativistic), has enabled us to study the dynamics of dense astroobjects in light of the modified gravitational effects. This EiBI theory imparts a new shape to the usual gravitational Poisson equation through the addition of a cosmological correction factor, termed as the EiBI gravity parameter. A systematic inclusion of this gravity in the basic structure equation could lead to a realistic picture of the existing solar models free from any end-stage singularity. A theoretic model is accordingly proposed to investigate the effect of the EiBI gravity on the Gravito-Electrostatic Sheath (GES) formalism of the equilibrium solar plasma structure. This study shows that the GES-based solar plasma dynamics is noticeably modified against the previously reported Newtonian GES-model studies. An equilibrium bounded solution for the solar self-gravity shows the EiBI-modified solar surface boundary (SSB) to exist at a new helio-centric radial location $ξ= 4$ (on the Jeansean scale). It is found that the EiBI gravity shifts the present SSB outwards by 14.28% relative to the original Newtonian SSB. The EiBI-modified gravity effects on diverse relevant solar parameters, such as the gravito-electrostatic potentials, fields, and Mach numbers, are illustratively analyzed. It is anticipated that our analyses could be applied further to see the solar plasma equilibrium and fluctuation dynamics in realistically modified post-Newtonian gravity environments on both the bounded (interior) and unbounded (exterior) solar plasma scales.

gr-qc

Analytic model for sheath-plasma resonance in inverted fireballs

The sheath plasma resonance (SPR) in an inverted fireball (IFB) system is semi-analytically investigated using a generalized hydrodynamic isothermal model formalism. It incorporates the constitutive ionic fluid viscosity, inter-species collisions, and geometric curvature effects. The SPR stability is studied for an anodic (hollow, meshed) IFB for the first time against the traditional cathode-plasma arrangements of regular electrode (solid, smooth) fireballs. The SPR develops near a spherical electrode enclosed by a plasma sheath amid a given electric potential. A generalized linear quartic dispersion relation (DR) with diverse plasma multi-parametric coefficients is methodically derived using a standard normal mode analysis. The mathematical construction of the obtained DR roots confirms that only one feasible nonzero frequency mode exists (emerging in the IFB). This root existence is confirmed both analytically and numerically. This consequent SPR creates trapped acoustic fluctuations in the IFB plasmas because of the internal reflections at the sheath plasma boundary. Also, sensible parametric changes in the SPR features, with both plasma density and viscosity, are seen. A local condition for the SPR excitation and its subsequent transition to collective standing wave-like patterns in the IFBs is illustrated. A fair corroboration of our results with the earlier SPR experimental observations of standing wave-like eigenmode patterns (evanescent) strengthens the reliability of our study alongside new applicability.

physics.plasm-ph

Pulsational mode stability in complex EiBI-gravitating polarized astroclouds with (r, q)-distributed electrons

The pulsational mode of gravitational collapse (PMGC) originating from the combined gravito-electrostatic interaction in complex dust molecular clouds (DMCs) is a canonical mechanism leading to the onset of astronomical structure formation dynamics. A generalized semi-analytic model is formulated to explore the effects of the Eddington-inspired Born-Infeld (EiBI) gravity, non-thermal (r, q)-distributed electrons, and dust-polarization force on the PMGC stability concurrently. The thermal ions are treated thermo-statistically with the Maxwellian distribution law and the non-thermal electrons with the (r, q)-distribution law. The constitutive partially ionized dust grains are modeled in the fluid fabric. A spherical normal mode analysis yields a generalized linear PMGC dispersion relation. Its oscillatory and propagation characteristics are investigated in a reasonable numerical platform. It is found that an increase in the polarization force and positive EiBI parameter significantly enhances the instability, causing the DMC collapse and vice versa. The electron non-thermality spectral parameters play as vital stabilizing factors, and so on. Its reliability and applicability are finally outlined in light of astronomical predictions previously reported in the literature.

astro-ph.GA

A theoretic analysis of magnetoactive GES-based turbulent solar plasma instability

A recently reported gravito-electrostatic sheath (GES) model is procedurally applied to study the turbumagnetoactive helioseismic oscillation features on the entire bi-fluidic solar plasma system. The bounded solar interior plasma (SIP, internally self-gravitating) and the unbounded solar wind plasma (SWP, externally point-gravitating) are coupled through the interfacial diffused solar surface boundary (SSB) due to an exact gravito-electrostatic interplay. A numerical platform on the developed theoretic formalism reveals the evolution of both dispersive and non-dispersive features of the modified GES mode fluctuations in new parametric windows. Different colourspectral profiles exhibit important features of the GES-based SIP-SWP perturbations elaborately. It is illustratively shown that the thermostatistical GES stability depends mainly on the radial distance, magnetic field, equilibrium plasma density, and plasma temperature. We see that their dispersive features are more pertinently pronounced in the self-gravitational domains (SIP) than the electrostatic ones (SWP). Besides, different characteristic parameters with accelerating (or decelerating) and stabilizing (or destabilizing) effects influencing the entire solar plasma stability are illustratively portrayed. We speculate that, in the SIP, the long-wave (gravitational-like) helioseismic fluctuations become highly dispersive showing more propagatory nature than the shorter ones (acoustic-like). The short waves show more propagatory propensity than the longer ones in the SSB and SWP regime. The reliability of our proposed investigation is bolstered along with the tentative applicability and future scope in light of the current solar observational scenarios, such as SOHO, STEREO, SDO, PSP, and SolO.

astro-ph.SR

Acoustic waves in the Jovian dusty magnetosphere: A brief review and meta-analysis

The omnipresence of dust particulates in space and astrophysical plasmas has been attracting numerous researchers to study the collective excitation and propagation dynamics of different eigen-mode structures in diversifed astrocosmic circumstances for years. It includes planetary rings, interplanetary space, cometary tails, asteroid zones, planetary atmospheres, etc. The ubiquitous charged dust particulates possess collective degrees of dynamic freedom resulting in the excitation of relatively low-frequency modes, such as dust-ion-acoustic waves (DIAWs), dust-acoustic waves (DAWs), dust-Coulomb waves (DCWs), and so forth. An interesting prevalency of dusty plasma stability research lies in the Jovian magnetosphere (i.e., Jovian plasmas), embedded inside the supersonic solar wind. A brief review of the updated research works on dust-acoustic waves and related collective instability dynamics in the presence of trapped plasma particles is presented herein. The key aim of the proposed explorative meta-analysis is rooted in outlining concisely the main up-to-date investigations on such collective instability processes chronologically. An especial attention is given primarily to the thermostatistical distribution laws of the constitutive lighter electrons and ions against the heavier positively charged dust grains (microspheres). The trapping mechanism of both the lighter species (electrons+ions) is another additive feature revisited here properly. Finally, we clearly extrapolate a number of futuristic directions in light of sensible novelties with a wider scope, both horizontally as well as vertically.

physics.plasm-ph

Non-planar magnetoactive GES-based solar plasma stability

A laboratory plasma-wall interaction-based astrophysical gravito-electrostatic sheath (GES) model is methodologically applied to study the dynamic stability of the magnetoactive bi-fluidic solar plasma system in the presence of turbulence effect. The spherically symmetric GES-model formalism couples the solar interior plasma (SIP, internally self-gravitating, bounded) and the solar wind plasma (SWP, externally point-gravitating, unbounded) through the diffused solar surface boundary (SSB). A normal spherical mode ansatz results in a generalized linear quadratic dispersion relation depicting the modal fluctuations on both the SIP and SWP scales. A constructive numerical platform reveals the evolution of both dispersive and non-dispersive modal features of the modified-GES mode excitations. The reliability of the derived non-planar dispersion laws is concretized with the help of an exact analytic shape matching the previously reported results founded on the plane-wave approximation. It is found that the thermo-statistical GES stability depends mainly on the magnetic field, equilibrium plasma density, and plasma temperature. It is speculated that the dispersive features are more pronounced in the self-gravitational domains against the electrostatic ones. The magneto-thermal interplay introduces decelerating (accelerating) and destabilizing (stabilizing) influences on the SIP (SWP), and so forth. At last, we briefly indicate the applicability of the proposed analysis to understand diverse helioseismic activities from the collective plasma dynamical viewpoint in accordance with the recent astronomical observational scenarios reported in the literature.

astro-ph.SR

Fireball sheath instability

The evolutionary existence of plasma fireballs is a generic phenomenon realizable in diversified physical plasma-dominated circumstances starting from the laboratory to the astrocosmic scales of space and time. A fair understanding of such fireballs and associated instabilities is indeed needed to enrich astroplasmic communities from various perspectives of applied value. Naturally occurring plasma fireball events include novae, meteors, stellar structures, etc. We propose a theoretical model formalism to analyze the plasma fireball sheath (PFS) instability with the application of a quasi-linear perturbative analysis on the laboratory spatiotemporal scales. This treatment reduces the steady-state system into a unique second-order ordinary differential equation (ODE) on the perturbed electrostatic potential with variable multiparametric coefficients. A numerical illustrative platform to integrate this ODE results in an atypical set of peakon-type potential-field structures. It is noticed that both the potential and field associated with the peakonic patterns change significantly with the effective radial distance from the reference origin outwards. The variations are more pronounced at the center (steep, stiff) than that in the off-centric regions (non-steep, non-stiff). A colormap obtained with the triangulation of the potential-field correlation with the radial distance further confirms the PFS stability behaviors in a qualitative corroboration with the previous predictions reported in the literature. The applicability of our analysis in both the laboratory and astrocosmic contexts is finally indicated.

astro-ph.HE

Stability of nucleus-acoustic waves in completely degenerate white dwarf cores and their nearly degenerate ambience

We analyze the propagatory nucleus-acoustic wave (NAW) modes excitable in the completely degenerate (CD) core and in its nearly degenerate (ND) ambience of the ONe and CO white dwarfs (WDs). It is based on three-component spherical hydrodynamic quantum plasma consisting of tiny non-thermal quantum electrons, classical thermal light nuclear species (LNS), and classical thermal heavy nuclear species (HNS). The inner concentric layer-wise electronic pressures are judiciously modelled. The electronic energy distribution governed by the Fermi-Dirac (FD) thermostatistical distribution law involves both the thermodynamical temperature and chemical potential. Our exploration emphasizes on the transition state between the thermodynamical temperature and the Fermi temperature for the borderline regions of intermediate degeneracy. A normal spherical mode analysis procedurally yields a sextic generalized linear dispersion relation highlighting the plasma multiparametric dependency of the NAW-features. A numerical illustrative platform is constructed to investigate the full NAW propagatory and dispersive behaviours. We demonstrate that the NAW in ONe (CO) WDs exhibits sensible growth characteristics at near the transcritical (supercritical) wave zone. The temperature-sensitivity of the NAW-growth is more (less) prominent in ONe (CO) WDs. It could be hopefully useful to see the internal structure of compact astroobjects from the asteroseismic probe-perspective of collective quantum interaction processes.

astro-ph.SR