A5060890879- Astrophysical Phenomena and Observations
- Heat Transfer Mechanisms
- Computational Fluid Dynamics and Aerodynamics
- Pulsars and Gravitational Waves Research
- Cosmology and Gravitation Theories
- Gas Dynamics and Kinetic Theory
- Galaxies: Formation, Evolution, Phenomena
- Black Holes and Theoretical Physics
- Advanced Numerical Methods in Computational Mathematics
- Ionosphere and magnetosphere dynamics
- Electromagnetic Simulation and Numerical Methods
- High-Energy Particle Collisions Research
- Magnetic confinement fusion research
- Laser-Plasma Interactions and Diagnostics
- Astrophysics and Cosmic Phenomena
- Fluid Dynamics and Turbulent Flows
- Relativity and Gravitational Theory
- Spacecraft and Cryogenic Technologies
- Parallel Computing and Optimization Techniques
- Solar and Space Plasma Dynamics
- Numerical methods in engineering
- Geomagnetism and Paleomagnetism Studies
- Lightning and Electromagnetic Phenomena
- Earthquake Detection and Analysis
- Spectroscopy and Laser Applications
Indian Institute of Science Education and Research Kolkata
2022-2023
University of Notre Dame
2015-2020
Korea Astronomy and Space Science Institute
2020
S.N. Bose National Centre for Basic Sciences
2010-2015
History of Science Society
2015
Low- and intermediate-frequency quasi-periodic oscillations (QPOs) in black hole candidates are believed to be due of the Comptonizing regions an accretion flow. Assuming that general structure disc is a two-component advective flow (TCAF), we numerically simulate light curves emitted from for different rates find how QPO frequencies vary. We use standard Keplerian residing at equatorial plane as source soft photons. These photons, after suffering multiple scattering with hot electrons low...
We investigate the effects of cooling Compton cloud on outflow formation rate in an accretion disk around a black hole. carry out time-dependent numerical simulation where both hydrodynamics and radiative transfer processes are coupled together. consider two-component flow which Keplerian is immersed into accreting low-angular momentum (halo) The soft photons originate from inverse-Comptonized by electrons halo region between centrifugal pressure supported shocks horizon. run several cases...
We carry out a time dependent numerical simulation where both the hydrodynamics and radiative transfer are coupled together. consider two-component accretion flow in which Keplerian disk is immersed inside an accreting low angular momentum (halo) around black hole. The injected soft photons from reprocessed by electrons halo. show that presence of axisymmetric soft-photon source, spherically symmetric Bondi losses its symmetry becomes axisymmetric. was observed to slow down close axis formed...
A black hole accretion is necessarily transonic. In presence of sufficiently high viscosity and cooling effects, a low-angular momentum transonic flow can become standard Keplerian disc except close to the where it must pass through inner sonic point. However, if not everywhere efficient everywhere, cannot completely disc. this paper, we show results rigorous numerical simulations having vertically varying parameter (being highest on equatorial plane) optical depth dependent processes that...
We study time evolution of sub-Keplerian transonic accretion flows onto black holes using a general relativistic numerical simulation code. perform simulations around the having non-zero rotation. first compare one-dimensional results with theoretical and validate performance our Next, we present axisymmetric, two-dimensional advective flows. In literature, there is no solution which describes steady shock solutions in two dimensions. However, produce these centrifugal force supported waves...
We study time evolution of sub-Keplerian transonic accretion flows onto black holes using a general relativistic numerical simulation code. perform simulations in Schwarzschild spacetime. first compare one-dimensional results with theoretical and validate the performance our Next, we present axisymmetric, two-dimensional advective flows. find that even this case, for which no complete analysis is literature, steady state shock formation possible.
ABSTRACT There is a great need in several areas of astrophysics and space physics to carry out high order accuracy, divergence-free MHD simulations on spherical meshes. This requires us pay careful attention the interplay between mesh quality numerical algorithms. Methods have been designed that fundamentally integrate high-order isoparametric mappings with other accuracy algorithms are needed for geodesic The goal this paper document such implemented version RIEMANN code. fluid variables...
A black hole accretion may have both the Keplerian and sub-Keplerian component. In so-called Chakrabarti–Titarchuk scenario, component supplies low-energy (soft) photons while hot electrons which exchange their energy with soft through Comptonization or inverse processes. component, a shock is generally produced due to centrifugal force. The postshock region known as CENtrifugal pressure–supported BOundary Layer (CENBOL). this paper, we compute effects of thermal bulk motion on emitted from...
ABSTRACT We study the time evolution of sub-Keplerian transonic accretion flow on to a non-rotating black hole using three-dimensional, inviscid hydrodynamics simulation code. Prior two-dimensional simulations show that centrifugal barrier in accreting matter may temporarily halt nearly free-falling and produce stable, geometrically thick disc contain turbulent eddies. Our goal this work is investigate whether develops any instability because turbulence when we dynamically activate all three...
Abstract The small-scale turbulent dynamo is an important process contributing to the cosmic magnetization. In partially ionized astrophysical plasmas, growth of magnetic energy strongly depends on coupling state between ions and neutrals ion-neutral collisional damping effect. A new stage in a weakly medium was theoretically predicted by Xu & Lazarian. By carrying out 3D two-fluid simulation, we have for first time numerically confirmed physical conditions linear-in-time field strength...
Two Component Advective Flow (TCAF) successfully explains the spectral and tem- poral properties of outbursting or persistent sources. Images static TCAF with Compton cloud CENtrifugal pressure supported Boundary Layer (CENBOL) due to gravitational bending photons have been studied before. In this paper, we study time dependent images advective flows around a Schwarzschild black hole which include cooling effects Comptonization soft from Keplerian disks well as self-consistently produced...
In the magnetosphere of a rotating black hole, an inner Alfven critical surface (IACS) must be crossed by inflowing plasma. Inside IACS, waves are inward directed toward hole. The majority proper volume active region spacetime (the ergosphere) is inside IACS. charge and totally transverse momentum flux to both wave normal unperturbed magnetic field) determined exclusively polarization. Thus, it important for numerical simulations hole magnetospheres minimize dissipation waves. Elements...
Abstract Many important problems in astrophysics, space physics, and geophysics involve flows of (possibly ionized) gases the vicinity a spherical object, such as star or planet. The geometry system naturally favors numerical schemes based on mesh. Despite its orthogonality property, polar (latitude-longitude) mesh is ill suited for computation because singularity axis, leading to highly non-uniform distribution zone sizes. consequences are (a) loss accuracy due large variations aspect...
Abstract Magnetic fields advected along with low angular momentum accretion flows predominantly become toroidal owing to the strong azimuthal velocity close a black hole. We study self-consistently movements of these flux tubes inside an advective disk and how they dynamically influence flow. find that centrifugal barrier slows down radial motion tubes. In this case, large magnetic significant drag force escape vertical axis buoyancy. pressure rises hole and, together force, combats gravity....
Strong gravity in the immediate vicinity of compact objects (e.g., black holes, neutron stars) necessitates inclusion general relativistic effects. Traditionally, pseudo-Newtonian potential representation were favored to simulate fluid motion this region since that reduced calculation complexity. However, with advent easily implementable, reliable numerical algorithms and computer hardware, more research groups are shifting towards solutions dynamics equations. In work, we report our...