Dynamics of magnetic flux tubes in an advective flow around a black hole

Deb, Arnab; Giri, Kinsuk; Chakrabarti, Sandip K.

doi:10.1093/mnras/stx1721

Cited by 6 publications

(5 citation statements)

References 32 publications

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“…The rising MFT can be the seed for the formation of jets and outflows from accretion discs. Similar idea was considered by Chakrabarti & D'Silva (1994) and Deb et al (2017) in application to the accretion discs around black holes. The rate of vertical mass transport via buoyancy can be estimated as a mass of the flux tubes rising from the disc per unit of time.…”

Section: Mass and Magnetic Flux Loss Due To Buoyancy Of Flux Tubesmentioning

confidence: 78%

“…They have shown that magnetic tension leads to MFT collapse. Deb et al (2017) extended model of Chakrabarti & D'Silva (1994) to take into account timedependent evolution of the flow around the MFT.…”

Section: Introductionmentioning

confidence: 99%

“…Dudorov (1991) proposed that MFT can be a part of the molecular outflows in the star formation regions. Chakrabarti & D'Silva (1994) and Deb et al (2017) argued that the MFT can play a role in acceleration and collimation of jets from accretion discs of black holes. Formation of looplike magnetic structures above the discs due to magnetic buoyancy instability and magnetic reconnection can lead to burst acitivity and heating of the region above the disc (Galeev et al 1979;Stella & Rosner 1984;Schramkowski 1996;Miller & Stone 2000;Hirose & Turner 2011;Uzdensky 2013).…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of magnetic flux tubes in accretion discs of T Tauri stars

Dudorov

Khaibrakhmanov

Соболев

2019

Monthly Notices of the Royal Astronomical Society

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Dynamics of slender magnetic flux tubes (MFT) in the accretion discs of T Tauri stars is investigated. We perform simulations taking into account buoyant, aerodynamic and turbulent drag forces, radiative heat exchange between MFT and ambient gas, magnetic field of the disc. The equations of MFT dynamics are solved using Runge-Kutta method of the fourth order. The simulations show that there are two regimes of MFT motion in absence of external magnetic field. In the region r < 0.2 au, the MFT of radii 0.05 a 0 0.16 H (H is the scale height of the disc) with initial plasma beta of 1 experience thermal oscillations above the disc. The oscillations decay over some time, and MFT continue upward motion afterwards. Thinner or thicker MFT do not oscillate. MFT velocity increases with initial radius and magnetic field strength. MFT rise periodically with velocities up to 5-15 km s −1 and periods of 0.5 −10 yr determined by the toroidal magnetic field generation time. Approximately 20% of disc mass and magnetic flux can escape to disc atmosphere via the magnetic buoyancy over characteristic time of disc evolution. MFT dispersal forms expanding magnetized corona of the disc. External magnetic field causes MFT oscillations near the disc surface. These magnetic oscillations have periods from several days to 1-3 months at r < 0.6 au. The magnetic oscillations decay over few periods. We simulate MFT dynamics in accretion discs in the Chameleon I cluster. The simulations demonstrate that MFT oscillations can produce observed IR-variability of T Tauri stars.

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Section: Mass and Magnetic Flux Loss Due To Buoyancy Of Flux Tubesmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dynamics of magnetic flux tubes in accretion discs of T Tauri stars

Dudorov

Khaibrakhmanov

Соболев

2019

Monthly Notices of the Royal Astronomical Society

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“…Thus it is very important to study the effects of magnetic fields on the accretion and outflows. Following CD9 and DC94, Deb et al (2017) recently showed that a single flux tube may be able to collimate the jet and outflow coming out of the post-shock region. However they used a hydrodynamic code which treated the fields passively.…”

Section: Discussionmentioning

confidence: 97%

“…Thus, efforts are on to include magnetic field to this advective flow which naturally produces thick discs as used in earlier days. After the work of CD94 and DC94 where the disk variables were pre-determined, a recent work by Deb et al (2017) studied the motion of flux tubes in a hydrodynamic time dependent flow showing that the injection of a single flux tube increased the collimation of the jet as long as it did not escape. However, there was no attempt to study MHD flows or the effects of the fields on the dynamics of the accretion flow.…”

Section: Introductionmentioning

confidence: 99%

Effects of Magnetic Field Loops on the Dynamics of Advective Accretion Flows and Jets around a Schwarzschild Black Hole

Garain

Balsara

Chakrabarti

et al. 2020

ApJ

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Magnetic fields advected along with low angular momentum accretion flows predominantly become toroidal due to the strong azimuthal velocity close to a black hole. We study self-consistently the movements of these flux tubes inside an advective disc and how they dynamically influence the flow. We find that the centrifugal barrier slows down the radial motion of the flux tubes. In this case, the large magnetic flux tubes with a significant drag force escape along the vertical axis due to buoyancy. Magnetic pressure rises close to the black hole and together with the centrifugal force, it combats gravity. The tug-of-war among these forces causes the centrifugal pressure supported shock to oscillate radially. We study the effects of successive injection of flux tubes and find how the flux tube could be trapped inside the disc in regions of highest entropy. Most interestingly, the shock wave remains at its average location and is not destroyed. We show that the toroidal field loops contribute significantly to collimate and accelerate the outflows from the centrifugal barrier and suggest this mechanism to be a way to collimate and accelerate jets.

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Dynamics of Magnetic Flux Tubes in an Advective Flow Around Black Hole

Deb¹

2018

Astrophysics and Space Science Proceedings

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Dynamics of magnetic flux tubes in an advective flow around a black hole

Cited by 6 publications

References 32 publications

Dynamics of magnetic flux tubes in accretion discs of T Tauri stars

Dynamics of magnetic flux tubes in accretion discs of T Tauri stars

Effects of Magnetic Field Loops on the Dynamics of Advective Accretion Flows and Jets around a Schwarzschild Black Hole

Dynamics of Magnetic Flux Tubes in an Advective Flow Around Black Hole

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