The impact of non-ideal magnetohydrodynamic processes on discs, outflows, counter-rotation and magnetic walls during the early stages of star formation

This is the author accepted manuscript. The final version is available from the Royal Astronomical Society via the DOI in this recordData availability: The data for models iMHD and ohaMHD± are openly available from the University of Exeters institutional repository at https://doi.org/10.24378/exe.607. The data for the remaining models will be available upon reasonable request.Non-ideal magnetohydrodynamic (MHD) processes – namely Ohmic resistivity, ambipolar diffusion and the Hall effect – modify the early stages of the star formation process and the surrounding environment. Collectively, they have been shown to promote disc formation and promote or hinder outflows. But which non-ideal process has the greatest impact? Using three-dimensional smoothed particle radiation non-ideal MHD simulations, we model the gravitational collapse of a rotating, magnetised cloud through the first hydrostatic core phase to shortly after the formation of the stellar core. We investigate the impact of each process individually and collectively. Including any non-ideal process decreases the maximum magnetic field strength by at least an order of magnitude during the first core phase compared to using ideal MHD, and promotes the formation of a magnetic wall. When the magnetic field and rotation vectors are anti-aligned and the Hall effect is included, rotationally supported discs of r≥20 au form; when only the Hall effect is included and the vectors are aligned, a counter-rotating pseudo-disc forms that is not rotationally supported. Rotationally supported discs of r≤4 au form if only Ohmic resistivity or ambipolar diffusion are included. The Hall effect suppresses first core outflows when the vectors are anti-aligned and suppresses stellar core outflows independent of alignment. Ohmic resistivity and ambipolar diffusion each promote first core outflows and delay the launching of stellar core outflows. Although each non-ideal process influences star formation, these results suggest that the Hall effect has the greatest influence.European Union FP7University of St Andrew