Large resistivity in numerical simulations of radially self-similar outflows

TL;DR

This study explores how high resistivity in accretion disk coronae affects outflow structures, revealing three distinct magnetic field configurations as resistivity increases, with implications for understanding magnetic topology changes.

Contribution

First to determine conditions at the base of radially self-similar outflows in high resistivity regimes using simulations.

Findings

Identified three solution modes with increasing resistivity.

Magnetic field geometry transitions from collimated to pressed against the disk.

Final mode remains stable despite further resistivity increases.

Abstract

We investigate the differences between an outflow in a highly-resistive accretion disk corona, and the results with smaller or vanishing resistivity. For the first time, we determine conditions at the base of a two-dimensional radially self-similar outflow in the regime of very large resistivity. We performed simulations using the {\sc pluto} magnetohydrodynamics code, and found three modes of solutions. The first mode, with small resistivity, is similar to the ideal-MHD solutions. In the second mode, with larger resistivity, the geometry of the magnetic field changes, with a "bulge" above the super-fast critical surface. At even larger resistivities, the third mode of solutions sets in, in which the magnetic field is no longer collimated, but is pressed towards the disk. This third mode is also the final one: it does not change with further increase of resistivity. These modes describe topological change in a magnetic field above the accretion disk because of the uniform, constant Ohmic resistivity.