The Athena++ Adaptive Mesh Refinement Framework: Design and Magnetohydrodynamic Solvers

Stone, James M.; Tomida, Kengo; White, Christopher J.; Felker, Kyle Gerard

doi:10.3847/1538-4365/ab929b

Cited by 416 publications

(336 citation statements)

References 100 publications

Supporting

Mentioning

317

Contrasting

Unclassified

Order By: Relevance

“…These simulations are performed using the GRMHD code, ATHENA++ (White, Stone & Gammie 2016;Stone et al 2020). They are initialized using the torus solution of Fishbone & Moncrief (1976), in which u φ u t (in Boyer Lindquist coordinates) is constant.…”

Section: Simulations a B And Cmentioning

confidence: 99%

Looking for the underlying cause of black hole X-ray variability in GRMHD simulations

Bollimpalli

Mahmoud

Done

et al. 2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

ABSTRACT Long-term observations have shown that black hole X-ray binaries exhibit strong, aperiodic variability on time-scales of a few milliseconds to seconds. The observed light curves display various characteristic features like a lognormal distribution of flux and a linear rms–flux relation, which indicate that the underlying variability process is stochastic in nature. It is also thought to be intrinsic to accretion. This variability has been modelled as inward propagating fluctuations of mass accretion rate, although the physical process driving the fluctuations remains puzzling. In this work, we analyse five exceptionally long-duration general relativistic magnetohydrodynamic (GRMHD) simulations of optically thin, geometrically thick, black hole accretion flows to look for hints of propagating fluctuations in the simulation data. We find that the accretion profiles from these simulations do show evidence for inward propagating fluctuations below the viscous frequency by featuring strong radial coherence and positive time lags when comparing smaller to larger radii, although these time lags are generally shorter than the viscous time-scale and are frequency-independent. Our simulations also support the notion that the fluctuations in $\dot{M}$ build up in a multiplicative manner, as the simulations exhibit linear rms–mass flux relations, as well as lognormal distributions of their mass fluxes. When combining the mass fluxes from the simulations with an assumed emissivity profile, we additionally find broad agreement with observed power spectra and time lags, including a recovery of the frequency dependency of the time lags.

show abstract

Section: Simulations a B And Cmentioning

confidence: 99%

Looking for the underlying cause of black hole X-ray variability in GRMHD simulations

Bollimpalli

Mahmoud

Done

et al. 2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…Our simulation combines ray-tracing radiative transfer, realtime nonequilibrium thermochemistry, and full hydrodynamics calculations (based on a higher-order Godunov hydrodynamic solver Athena++; Stone et al 2020). The simulation is mostly based on our WD18 work, with a few modifications and improvements added for the higher dimensionality and the inclusion of He * .…”

Section: Basic Setupmentioning

confidence: 99%

Metastable Helium Absorptions with 3D Hydrodynamics and Self-consistent Photochemistry. I. WASP-69b, Dimensionality, X-Ray and UV Flux Level, Spectral Types, and Flares

Wang

Dai

2021

ApJ

View full text Add to dashboard Cite

The metastable helium (He * ) lines near 10830 Å are ideal probes of atmospheric erosion-a common phenomenon of close-in exoplanet evolution. A handful of exoplanet observations yielded well-resolved He * absorption features in transits, yet they were mostly analyzed with 1D isothermal models prescribing mass-loss rates. This work devises 3D hydrodynamics coevolved with ray-tracing radiative transfer and nonequilibrium thermochemistry. Starting from the observed stellar/planetary properties with reasonable assumptions about the host's high-energy irradiation, we predict from first principles the mass-loss rate, the temperature and ionization profiles, and 3D outflow kinematics. Our simulations well reproduce the observed He * line profiles and light curves of WASP-69b. We further investigate the dependence of He * observables on simulation conditions and host radiation. The key findings are as follows: (1) Simulations reveal a photoevaporative outflow (∼0.55 M ⊕ Gyr −1 ; 10 11 g s −1 ) for WASP-69b without a prominent comet-like tail, consistent with the symmetric transit shape. (2) 3D simulations are mandatory for hydrodynamic features, including Coriolis force, advection, and kinematic line broadening. (3) EUV (>13.6 eV) photons dominate photoevaporative outflows and populate He * via recombination; FUV is also detrimental by destroying He * ; X-ray plays a secondary role. (4) K stars hit the sweet spot of EUV/far-UV balance for He * line observation, while G and M stars are also worthy targets. (5) Stellar flares create characteristic responses in the He * line profiles.

show abstract

“…The algorithm has been implemented in the publicly available MHD code Athena?? (Stone et al 2020). Thomas and Pfrommer (2019) developed a new macroscopic transport theory, which includes both diffusion and streaming of CRs in the selfconfinement picture.…”

Section: Unified Alfvén Wave Regulated Cr Transportmentioning

confidence: 99%

Simulations of cosmic ray propagation

Hanasz

Strong

Girichidis

2021

Living Rev Comput Astrophys

View full text Add to dashboard Cite

We review numerical methods for simulations of cosmic ray (CR) propagation on galactic and larger scales. We present the development of algorithms designed for phenomenological and self-consistent models of CR propagation in kinetic description based on numerical solutions of the Fokker–Planck equation. The phenomenological models assume a stationary structure of the galactic interstellar medium and incorporate diffusion of particles in physical and momentum space together with advection, spallation, production of secondaries and various radiation mechanisms. The self-consistent propagation models of CRs include the dynamical coupling of the CR population to the thermal plasma. The CR transport equation is discretized and solved numerically together with the set of MHD equations in various approaches treating the CR population as a separate relativistic fluid within the two-fluid approach or as a spectrally resolved population of particles evolving in physical and momentum space. The relevant processes incorporated in self-consistent models include advection, diffusion and streaming propagation as well as adiabatic compression and several radiative loss mechanisms. We discuss, applications of the numerical models for the interpretation of CR data collected by various instruments. We present example models of astrophysical processes influencing galactic evolution such as galactic winds, the amplification of large-scale magnetic fields and instabilities of the interstellar medium.

show abstract

The Athena++ Adaptive Mesh Refinement Framework: Design and Magnetohydrodynamic Solvers

Cited by 416 publications

References 100 publications

Looking for the underlying cause of black hole X-ray variability in GRMHD simulations

Looking for the underlying cause of black hole X-ray variability in GRMHD simulations

Metastable Helium Absorptions with 3D Hydrodynamics and Self-consistent Photochemistry. I. WASP-69b, Dimensionality, X-Ray and UV Flux Level, Spectral Types, and Flares

Simulations of cosmic ray propagation

Contact Info

Product

Resources

About