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| Paper: |
Radiatively Efficient Magnetized Bondi Accretion |
| Volume: |
459, 6th International Conference of Numerical Modeling of Space Plasma Flows (ASTRONUM 2011) |
| Page: |
61 |
| Authors: |
Cunningham, A. J.; McKee, C. F.; Klein, R. I.; Krumholz, M. R.; Teyssier, R. |
| Abstract: |
We have carried out a numerical study of the effect of large scale
magnetic fields on the rate of accretion from a uniform, isothermal
gas onto a resistive, stationary point mass. Only mass, not magnetic
flux, accretes onto the point mass. The simulations for this study
avoid complications arising from boundary conditions by keeping the
boundaries far from the accreting object. Our simulations leverage
adaptive refinement methodology to attain high spatial fidelity close
to the accreting object. Our results are particularly relevant to the
problem of star formation from a magnetized molecular cloud in which
thermal energy is radiated away on time scales much shorter than the
dynamical time scale. Contrary to the adiabatic case, our simulations
show convergence toward a finite accretion rate in the limit in which
the radius of the accreting object vanishes, regardless of magnetic
field strength. For very weak magnetic fields, the accretion rate
first approaches the Bondi value and then drops by a factor ∼ 2
as magnetic flux builds up near the point mass. For strong magnetic
fields, the steady-state accretion rate is reduced by a factor ∼
0.2 β1/2 compared to the Bondi value, where β is the
ratio of the gas pressure to the magnetic pressure. We give a simple
expression for the accretion rate as a function of the magnetic field
strength. |
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