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SPMHD simulations of protostellar outflows with misaligned magnetic fields


Previous work (e.g. Tricco, Bate, and Price 2012 ) has been limited by numerics to only using larger sink particles (> 5 AU) and has not considered regimes where the magnetic field and rotation axes are misaligned. Here we have developed a small modification to our SPMHD method to ensure numerical stability and thereby performed a comparable simulation that that in TBP2012 but with a 1 AU sink particle and with six different field geometries. An initial overview of this work was presented on a poster at the 2014 DiRAC Science Day in Durham.

Formal Abstract and Publication Details

We have developed a modified form of the equations of smoothed particle magnetohydrodynamics which are stable in the presence of very steep density gradients. Using this formalism, we have performed simulations of the collapse of magnetised molecular cloud cores to form protostars and drive outflows. Our stable formalism allows for smaller sink particles (< 5 AU) than used previously and the investigation of the effect of varying the angle, ϑ, between the initial field axis and the rotation axis. The nature of the outflows depends strongly on this angle: jet-like outflows are not produced at all when ϑ > 30°, and a collimated outflow is not sustained when ϑ > 10°. No substantial outflows of any kind are produced when ϑ > 60°. This may place constraints on the geometry of the magnetic field in molecular clouds where bipolar outflows are seen.

Published in Monthly Notices of the Royal Astronomical Society, (July 21, 2015) 451 (1) 288-299 (doi:10.1093/mnras/stv957)

E-print available on the arXiv as arXiv:1504.08322 and bibliographic data on the ADS.

The dataset used to produce the paper is available in ORE.

Animations and Images

Under construction - more images will follow

6 plots of column density at t = 26650 yrs

In this animation we show the time evolution for six protostellar collapse models, with ϑ ranging from 0° (i.e. fully aligned) to 90°. The very different evolution between the models can be clearly seen.
MP4 file (1980x1080 pixels, 1.7 MB)


The animations and images on this page are © 2014-15 Benjamin Lewis, Matthew Bate, and Daniel Price and are made available under a Creative Commons Attribution-NonCommercial-ShareAlike (2.0 UK: England & Wales) license.

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