Magnetohydrodynamic convection in accretion discs
| Autor: | Loren E. Held, Henrik N. Latter |
|---|---|
| Přispěvatelé: | Apollo - University of Cambridge Repository |
| Rok vydání: | 2021 |
| Předmět: |
astro-ph.HE
High Energy Astrophysical Phenomena (astro-ph.HE) Convection Physics Angular momentum astro-ph.SR 010308 nuclear & particles physics Turbulence FOS: Physical sciences Astronomy and Astrophysics Perfect gas Mechanics 01 natural sciences Physics::Fluid Dynamics Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science Magnetorotational instability 0103 physical sciences Thermal Astrophysics::Solar and Stellar Astrophysics Magnetohydrodynamics Astrophysics - High Energy Astrophysical Phenomena 010303 astronomy & astrophysics Solar and Stellar Astrophysics (astro-ph.SR) Convection cell |
| Zdroj: | Monthly Notices of the Royal Astronomical Society |
| ISSN: | 1365-2966 0035-8711 |
| DOI: | 10.1093/mnras/stab974 |
| Popis: | Convection has been discussed in the field of accretion discs for several decades, both as a means of angular momentum transport and also because of its role in controlling discs' vertical structure via heat transport. If the gas is sufficiently ionized and threaded by a weak magnetic field, convection might interact in non-trivial ways with the magnetorotational instability (MRI). Recently, vertically stratified local simulations of the MRI have reported considerable variation in the angular momentum transport, as measured by the stress to thermal pressure ratio $\alpha$, when convection is thought to be present. Although MRI turbulence can act as a heat source for convection, it is not clear how the instabilities will interact dynamically. Here we aim to investigate the interplay between the two instabilities in controlled numerical experiments, and thus isolate the generic features of their interaction. We perform vertically stratified, 3D MHD shearing box simulations with a perfect gas equation of state with the conservative, finite-volume code PLUTO. We find two characteristic outcomes of the interaction between the two instabilities: straight MRI and MRI/convective cycles, with the latter exhibiting alternating phases of convection-dominated flow (during which the turbulent transport is weak) and MRI-dominated flow. During the latter phase we find that $\alpha$ is enhanced by nearly an order of magnitude, reaching peak values of $\sim 0.08$. In addition, we find that convection in the non-linear phase takes the form of large-scale and oscillatory convective cells. Convection can also help the MRI persist to lower Rm than it would otherwise do. Finally we discuss how our results help interpret simulations of Dwarf Novae. Comment: Accepted for publication in MNRAS (23 pages, 14 figures, 1 table) |
| Databáze: | OpenAIRE |
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