scholarly journals Relativistic Adiabatic Shocks in Accretion Flows

2000 ◽  
Vol 195 ◽  
pp. 381-384
Author(s):  
D. M. Caditz ◽  
S. Tsuruta
Keyword(s):  
Steady State ◽  
Energy Density ◽  
Shock Front ◽  
Radiation Pressure ◽  
Emission Characteristics ◽  
Jump Conditions ◽  
Relativistic Plasmas ◽  
Accretion Flows ◽  
And Shock Waves ◽  
Effects Of Radiation

Accretion flows onto compact astronomical sources are likely to be supersonic, and shock waves may therefore be common in such flows. Plasma passing through a shock front will be compressed and heated according to the jump conditions across the shock discontinuity. Shocks in accretion flows may therefore have important consequences for the flow structure and emission characteristics. The equations governing adiabatic (nonradiative) shocks in relativistic plasmas are presented including the effects of radiation pressure and energy density, and pair equilibria in the postshock flow. We find that postshock states for accretion flows within cool, optically thick, accretion-driven sources such as AGN become radiation- or pair-dominated, and the postshock plasma will likely become optically thin before returning to steady-state conditions.

Radiative shocks in spherical accretion

2019 ◽  
Vol 71 (5) ◽  
Author(s):  
Jun Fukue
Keyword(s):  
Radiation Pressure ◽  
Gravitational Effect ◽  
Curvature Effect ◽  
Jump Conditions ◽  
Accretion Flows ◽  
Radiative Shocks ◽  
Starting Point ◽  
Shock Region ◽  
Radiative Diffusion ◽  
Shock Mach Number

ABSTRACT In order to explore various aspects of radiative shocks, we examine standing radiative shock waves in spherical accretion flows onto a central gravitating body under the equilibrium diffusion approximation. In contrast to the usual one-dimensional shock, in radiative shocks a radiative precursor appears in the pre-shock region before the shock front, due to the radiative diffusion effect. Furthermore, in spherical flows around a central object the gravitational potential varies in this radiative precursor, and a curvature effect also exists. We first formulate such radiative shocks in spherical flows, derive the overall jump conditions, and solve the structure of the radiative precursor for both the gas and radiation pressure dominated cases. Since the jump conditions contain the coordinates of both ends of the radiative precursor, we must obtain both the solution and the endpoints of the precursor simultaneously. We find that the gravitational effect is not significant, although it cannot be ignored. The curvature effect exerts a strong influence on the structure and width of the precursor. The precursor starting point x1 normalized by the shock radius is roughly expressed by $x_1={\cal M}_1^{1/7}$ for a radiation pressure dominated shock, while $x_1=1.21^{({\cal M}_1-1)}$ for a gas pressure one, where ${\cal M}_1$ is the pre-shock Mach number.

scholarly journals On the Jump Conditions for Shock Waves in Condensed Materials

2021 ◽  
Author(s):  
R K Anand
Keyword(s):  
Stainless Steel ◽  
Mach Number ◽  
Shock Front ◽  
Particle Velocity ◽  
Mass Density ◽  
Jump Conditions ◽  
Condensed Material ◽  
Material Parameters ◽  
Stainless Steel 304 ◽  
Condensed Materials

Abstract In this article, we have proposed Rankine–Hugoniot (RH) boundary conditions at the normal shock-front which is passing through the condensed material. These RH conditions are quite general, and their convenient forms for the particle velocity, mass density, pressure and temperature have been presented in terms of the upstream Mach number, and the material parameters for the weak and the strong shocks, respectively. Finally, the effects on the mechanical quantities of the shock compressed materials e.g. titanium Ti6Al4V, stainless steel 304, aluminum 6061-T6, etc. have been discussed.

Optomechanical Interactions

2020 ◽  
pp. 105-128
Author(s):  
Ivan Favero
Keyword(s):  
Radiation Pressure ◽  
Hamiltonian Formulation ◽  
Mechanical Action ◽  
Gradient Force ◽  
Optical Forces ◽  
Hamiltonian Description ◽  
Optomechanical Systems ◽  
Equal Footing ◽  
Scientific Potential ◽  
Effects Of Radiation

Light exerts mechanical action on matter through various mechanisms, the most famous being radiation pressure, with the associated picture of a photon bouncing on a perfectly reflective movable mirror and transferring twice its momentum. But still today, unambiguously observing the effects of radiation pressure remains a challenge. In the quantum domain, the radiation pressure interaction between a moving mirror and light stored in a cavity accepts a simple Hamiltonian formulation. But this Hamiltonian description is sometimes oversimplified and underestimates or misses other mechanical effects of light accompanying radiation pressure in experiments. In this chapter, we will not only address radiation pressure but also other relevant optical forces such as the optical gradient force, electrostriction, or the photothermal and optoelectronic forces, which are key in micro- and nanoscale devices and must all be controlled on an equal footing to fully harness the technological and scientific potential of miniature optomechanical systems.

scholarly journals Shocks in relativistic viscous accretion flows around Kerr black holes

2019 ◽  
Vol 488 (2) ◽  
pp. 2412-2422 ◽  
Author(s):  
Indu K Dihingia ◽  
Santabrata Das ◽  
Debaprasad Maity ◽  
Anuj Nandi
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Shock Front ◽  
Critical Point ◽  
Parameter Space ◽  
Accretion Flows ◽  
Flow Parameters ◽  
Flow Motion ◽  
Present Formalism ◽  
Kerr Black Holes

ABSTRACT We study the relativistic viscous accretion flows around the Kerr black holes. We present the governing equations that describe the steady-state flow motion in full general relativity and solve them in 1.5D to obtain the complete set of global transonic solutions in terms of the flow parameters, namely specific energy (${\mathcal E}$), specific angular momentum (${\mathcal L}$), and viscosity (α). We obtain a new type of accretion solution which was not reported earlier. Further, we show for the first time to the best of our knowledge that viscous accretion solutions may contain shock waves particularly when flow simultaneously passes through both inner critical point (rin) and outer critical point (rout) before entering into the Kerr black holes. We examine the shock properties, namely shock location (rs) and compression ratio (R, the measure of density compression across the shock front) and show that shock can form for a large region of parameter space in ${\cal L}\!-\!{\cal E}$ plane. We study the effect of viscous dissipation on the shock parameter space and find that parameter space shrinks as α is increased. We also calculate the critical viscosity parameter (αcri) beyond which standing shock solutions disappear and examine the correlation between the black hole spin (ak) and αcri. Finally, the relevance of our work is conferred where, using rs and R, we empirically estimate the oscillation frequency of the shock front (νQPO) when it exhibits quasi-periodic (QP) variations. The obtained results indicate that the present formalism seems to be potentially viable to account for the QPO frequency in the range starting from milli-Hz to kilo-Hz as $0.386~{\rm Hz}\le \nu _{\mathrm{ QPO}} (\frac{10\, \mathrm{M}_\odot }{M_{\mathrm{ BH}}}) \le 1312$ Hz for ak = 0.99, where MBH stands for the black hole mass.

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