scholarly journals Dynamical structure of highly eccentric discs with applications to tidal disruption events

2020 ◽  
Vol 500 (3) ◽  
pp. 4110-4125
Author(s):  
Elliot M Lynch ◽  
Gordon I Ogilvie
Keyword(s):  
Thermal Instability ◽  
Vertical Structure ◽  
Scale Height ◽  
Accretion Discs ◽  
Radiative Cooling ◽  
Dynamical Structure ◽  
Tidal Disruption ◽  
The Subject ◽  
Stable Solutions ◽  
Physical Quantities

ABSTRACT Whether tidal disruption events circularize or accrete directly as highly eccentric discs is the subject of current research and appears to depend sensitively on the disc thermodynamics. One aspect of this problem that has not received much attention is that a highly eccentric disc must have a strong, non-hydrostatic variation of the disc scale height around each orbit. As a complement to numerical simulations carried out by other groups, we investigate the dynamical structure of TDE discs using the non-linear theory of eccentric accretion discs. In particular, we study the variation of physical quantities around each elliptical orbit, taking into account the dynamical vertical structure, as well as viscous dissipation and radiative cooling. The solutions include a structure similar to the nozzle-like structure seen in simulations. We find evidence for the existence of the thermal instability in highly eccentric discs dominated by radiation pressure. For thermally stable solutions many of our models indicate a failure of the α-prescription for turbulent stresses. We discuss the consequences of our results for the structure of eccentric TDE discs.

scholarly journals Importance of magnetic fields in highly eccentric discs with applications to tidal disruption events

2021 ◽  
Author(s):  
Elliot M Lynch ◽  
Gordon I Ogilvie
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Vertical Structure ◽  
Tidal Disruption ◽  
The Subject ◽  
Stress Models

Abstract Whether tidal disruption events (TDEs) circularise or accrete directly as a highly eccentric disc is the subject of current research and appears to depend sensitively on the disc thermodynamics. In a previous paper we applied the theory of eccentric discs to TDE discs using an α −prescription for the disc stress, which leads to solutions that exhibit extreme, potentially unphysical, behaviour. In this paper we further explore the dynamical vertical structure of highly eccentric discs using alternative stress models that are better motivated by the behaviour of magnetic fields in eccentric discs. We find that the presence of a coherent magnetic field has a stabilising effect on the dynamics and can significantly alter the behaviour of highly eccentric radiation dominated discs. We conclude that magnetic fields are important for the evolution of TDE discs.

scholarly journals The Physics of Accretion Discs, Winds and Jets in Tidal Disruption Events

2021 ◽  
Vol 217 (1) ◽  
Author(s):  
Jane Lixin Dai ◽  
Giuseppe Lodato ◽  
Roseanne Cheng
Keyword(s):  
Accretion Discs ◽  
Tidal Disruption

scholarly journals The vertical structure of T Tauri accretion discs

2003 ◽  
Vol 400 (1) ◽  
pp. 185-202 ◽  
Author(s):  
R. Lachaume ◽  
F. Malbet ◽  
J.-L. Monin
Keyword(s):  
Vertical Structure ◽  
Accretion Discs ◽  
T Tauri

Alpha Beta Discs

1983 ◽  
Vol 72 ◽  
pp. 55-67
Author(s):  
G.T. Bath ◽  
A.C. Edwards ◽  
V.J. Mantle
Keyword(s):  
Mass Transfer ◽  
Vertical Structure ◽  
Accretion Discs ◽  
Time Dependent ◽  
Simple Method ◽  
Dwarf Nova ◽  
Physical Conditions ◽  
Alpha Beta ◽  
Symbiotic Binaries

Following earlier work of Lynden-Bell & Pringle (1974) and Lightman (1974a, 1974b), Bath & Pringle (1981) have presented a simple method for studying the time-dependent evolution of viscous accretion discs. These models are axisymmetrlc, with the vertical structure reduced to integrated averages of local physical conditions. Published work examines models of dwarf nova eruptions driven by mass transfer bursts (Bath & Pringle 1981 – Paper I), eruptions produced by global viscous changes within the disc (Bath & Pringle 1982a Paper II), and the time-dependent properties of giant discs in symbiotic binaries (Bath & Pringle 1982b – Paper III).

scholarly journals X-Ray Heated Accretion Discs Around Stellar Mass Black Holes

2004 ◽  
Vol 194 ◽  
pp. 200-201
Author(s):  
Ivan Hubeny ◽  
Dayal T. Wickramasinghe
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Vertical Structure ◽  
Black Body ◽  
Incident Radiation ◽  
Accretion Discs ◽  
Distribution Models ◽  
Solar Mass ◽  
X Ray ◽  
Low Mass

We investigate the effects of irradiation on the vertical structure of accretion discs around black holes and its impact on the emergent energy distribution. Models are presented for a 10 Solar mass black hole in a low mass X-ray binary assuming a black body spectrum for the incident radiation. We show that for a disc annulus at a given radius, the spectra become increasingly distorted as the incident flux increases relative to the viscously generated heating flux in the disc. Significant effects are apparent for rings even at distances of ~ 10,000 Schwarzschild radii from the black hole for realistic dilution factors.

Vectors for Beginners

1921 ◽  
Vol 14 (7) ◽  
pp. 355-361
Author(s):  
Joseph B. Reynolds
Keyword(s):  
Displacement Velocity ◽  
Vector Method ◽  
Preparatory Schools ◽  
Acceleration Force ◽  
The Subject ◽  
Physical Quantities

The vector idea is so common in the study of science and the vector method so easy and effectual in application that students in preparatory schools should acquire an understanding of the subject. Its importance is emphasized when we recall that displacement, velocity, acceleration, force, electric cnrrent, stresses, strains and many other physical quantities can be correctly represented by vectors.

Retrospective and Prospective of the Subject’s Principle in the Research of Thinking in the Rubinstein’s School

2021 ◽  
pp. 75-81
Author(s):  
Ksenia A. Abulkhanova ◽  
Keyword(s):  
Vertical Structure ◽  
Psychological Theory ◽  
Russian Academy Of Sciences ◽  
Permanent Employee ◽  
The Subject ◽  
Thinking Process ◽  
Academy Of Sciences

The article compares two lines of development of S.L. Rubinstein's theory. The first of them is associated with the activities of Rubinstein's student and permanent employee, after his death, the director of the Psychological Institute of the Russian Academy of Sciences, A.V. Brushlinsky, the second-with the activities of the last student of S.L. Rubinstein, D.B. Bogoyavlenskaya. If Brushlinsky introduces the concept of non-instantaneous insight, which marks the insight prepared by the previous thinking process, then Bogoyavlenskaya justifies the instantaneity of insight, describing the “vertical” structure of the thinking process and the corresponding language; Brushlinsky introduces the term “sought” to denote the goal of finding a solution to the problem-Bogoyavlenskaya goes further and reveals the ability of the subject to develop activities on his initiative after finding such a solution; Brushlinsky develops the subject-activity approach – Bogoyavlenskaya implements the principle of Rubinstein’s creative autoactivity [1922], developing the philosophical and psychological theory of the teacher and its methodological richness.

Multiphysics circuit of a magnetostrictive energy harvesting device

2017 ◽  
Vol 28 (17) ◽  
pp. 2317-2330 ◽  
Author(s):  
Carmine S Clemente ◽  
Abdelmomen Mahgoub ◽  
Daniele Davino ◽  
Ciro Visone
Keyword(s):  
Energy Harvesting ◽  
Equivalent Circuit ◽  
Permanent Magnets ◽  
Nonlinear Functions ◽  
Circuit Simulator ◽  
The Subject ◽  
Full Coupling ◽  
Resistive Loads ◽  
Energy Harvesting Devices ◽  
Physical Quantities

Kinetic energy harvesting devices based on magnetostrictive materials are composed of several parts, for dealing with multiphysics, including mechanical, magnetic, and electric quantities. An effective method to simulate the effects of different working conditions is important to fully exploit such devices. The aim of this paper is to present an equivalent circuit that can be identified with standard measurements on the device and simulated with a standard circuit simulator, such as Spice. The circuit is a nonlinear three-port circuit, related to the mechanical, magnetic, and electrical parts of the device. Unlike many of the published papers on the subject, the magneto-mechanical modeling is quite realistic and exploits nonlinear functions and the full coupling among the involved physical quantities of the employed magnetostrictive material. The nonlinear equivalent circuit is preliminarily validated on a concept device with permanent magnets biasing on a Stress Annealed Galfenol rod. Experimental data with different resistive loads and magnetic biasing are considered and compared with simulation outputs, in terms of the RMS voltage and harvested power.

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