Can non-ideal magnetohydrodynamics solve the magnetic braking catastrophe? (dataset)
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Price, Daniel J
Monthly Notices of the Royal Astronomical Society
University of Exeter
We investigate whether or not the low ionization fractions in molecular cloud cores can solve the ‘magnetic braking catastrophe’, where magnetic fields prevent the formation of circumstellar discs around young stars. We perform three-dimensional smoothed particle non- ideal magnetohydrodynamics (MHD) simulations of the gravitational collapse of one solar mass molecular cloud cores, incorporating the effects of ambipolar diffusion, Ohmic resistivity and the Hall effect alongside a self-consistent calculation of the ionization chemistry assuming 0.1 μm grains. When including only ambipolar diffusion or Ohmic resistivity, discs do not form in the presence of strong magnetic fields, similar to the cases using ideal MHD. With the Hall effect included, disc formation depends on the direction of the magnetic field with respect to the rotation vector of the gas cloud. When the vectors are aligned, strong magnetic braking occurs and no disc is formed. When the vectors are anti-aligned, a disc with radius of 13 au can form even in strong magnetic when all three non-ideal terms are present, and a disc of 38 au can form when only the Hall effect is present; in both cases, a counter-rotating envelope forms around the first hydrostatic core. For weaker, anti-aligned fields, the Hall effect produces massive discs comparable to those produced in the absence of magnetic fields, suggesting that planet formation via gravitational instability may depend on the sign of the magnetic field in the precursor molecular cloud core.
This is all the data created for Wurster, Price & Bate (2016). This dataset was created using the SPHMD code Phantom and included a precursor to the NICIL library (Wurster 2016) to calculate the non-ideal MHD coefficients. The data and important files have been uploaded; the data files can be read with either Phantom, or with the graphics programme Splash. The filenames represent the original path and the simulation, and have the prefix WPB2016_pdata_. The second component to the filename is 1e6 (models with 1e6 particles in the sphere) or 3e5 (models with 1e6 particles in the sphere) and the third component is the simulation name. Typically, the model name has the form ABC, where A=ii,ni,nim for ideal, non-ideal with Bz, non-ideal with -Bz, respectively; B=o,h,a,oha for ohmic,hall,ambipolar,ohmic+hall+ambipolar, respectively; C=B,Q,C,D,P mu0=10,7.5,5,5,hydro, respectively. Ideal runs do not have a B part to the name.
MNRAS, 457:1037-1061, March 2016