Comparison between axisymmetric numerical magnetohydrodynamical simulations and self-similar solutions of jet-emitting disks

TL;DR

This study compares axisymmetric numerical MHD simulations of jet-emitting disks with analytical self-similar solutions, finding near-perfect agreement and confirming the analytical models as reliable representations of accretion-ejection physics.

Contribution

It provides the first thorough comparison between time-dependent numerical simulations and analytical self-similar solutions of jet-emitting disks, resolving previous discrepancies.

Findings

Numerical and analytical solutions show almost perfect agreement.

Simulations confirm JEDs as dynamical attractors.

Self-similar solutions are validated as effective models.

Abstract

Turbulent accretion disks threaded by a large-scale vertical field near equipartition can drive tenuous and fast self-confined jets. Self-similar solutions of these jet-emitting disks (JEDs) have been known for a long time and provide the distributions of all physical quantities, from the turbulent disk to the asymptotic regime of ideal magnetohydrodynamic (MHD) jets. However, a thorough comparison with time-dependent numerical simulations has never been achieved, mostly because mass-loss rates found in simulations were always larger than those found analytically. This tension may have cast doubt on the analytical approach, the numerical one, or both. Our goal is to bridge the gap between these two complementary approaches and settle this long-standing issue. We performed 2.5D (axisymmetric) simulations of resistive and viscous accretion disks described by the same parameter sets as analytical JED solutions. The results demonstrate an almost perfect agreement between the numerical and analytical solutions, thereby resolving the previously observed tension. The simulations also confirm that JEDs behave as dynamical attractors: starting from different initial conditions, the system consistently converges toward the expected steady-state solution. This work demonstrates that self-similar solutions provide valuable insights into accretion-ejection physics. However, as 2.5D numerical simulations which rely on alpha-prescriptions, they strongly depend on the assumptions made for turbulent terms. In contrast, 3D simulations capture the turbulence, but become prohibitively expensive when modeling large-scale astrophysical systems. We advocate for the use of global 3D simulations to investigate turbulence and to derive physically motivated prescriptions for use in 2.5D studies.