Resistive MHD jet simulations with large resistivity

TL;DR

This paper presents resistive MHD jet simulations exploring how different resistivity regimes affect outflow dynamics, revealing significant deviations from ideal MHD in high-resistivity conditions and identifying two distinct solution regimes.

Contribution

It introduces a new resistive parameter Rb alongside Rm and demonstrates the existence of two solution regimes in resistive MHD jet simulations, highlighting the impact of resistivity on outflow behavior.

Findings

Low-resistivity regime aligns with ideal MHD results.

High-resistivity regime shows periodic and significantly different behavior.

Identification of two distinct solution regimes based on resistivity levels.

Abstract

Axisymmetric resistive MHD simulations for radially self-similar initial conditions are performed, using the NIRVANA code. The magnetic diffusivity could occur in outflows above an accretion disk, being transferred from the underlying disk into the disk corona by MHD turbulence (anomalous turbulent diffusivity), or as a result of ambipolar diffusion in partially ionized flows. We introduce, in addition to the classical magnetic Reynolds number Rm, which measures the importance of resistive effects in the induction equation, a new number Rb, which measures the importance of the resistive effects in the energy equation. We find two distinct regimes of solutions in our simulations. One is the low-resistivity regime, in which results do not differ much from ideal-MHD solutions. In the high-resistivity regime, results seem to show some periodicity in time-evolution, and depart significantly from the ideal-MHD case. Whether this departure is caused by numerical or physical reasons is of considerable interest for numerical simulations and theory of astrophysical outflows and is currently investigated.