| Περίληψη |
Non-ideal magnetohydrodynamic (MHD) effects are thought to be a crucial component of
the star-formation process. Numerically, several complications render the study of non-ideal
MHD effects in 3-dimensional (3D) simulations extremely challenging and hinder our efforts
of exploring a large parameter space. Here, we aim to overcome such challenges by proposing
a novel, physically-motivated method to model non-ideal MHD effects. We perform a number
of 2D axisymmetric non-ideal MHD simulations of collapsing prestellar cores and clouds
with non-equilibrium chemistry and leverage upon previously-published results from similar
simulations with different physical conditions. We utilize these simulations to develop a
multivariate interpolating function to predict the ionization fraction in each region of the
cloud depending on the local physical conditions. We subsequently use analytically-derived,
simplified expressions to calculate the resistivities of the cloud in each grid cell. Therefore,
in our new approach the resistivities are calculated without the use of a chemical network.
We benchmark our method against additional 2D axisymmetric non-ideal MHD simulations
with random initial conditions and 3D non-ideal MHD simulations with non-equilibrium
chemistry. We find excellent quantitative and qualitative agreement between our approach
and the “full” non-ideal MHD simulations both in terms of the spatial structure of the
simulated clouds and regarding their time evolution. At the same time, we achieve a factor
of ∼ 102 − 103 increase in computational speed. We trust that our method will be useful for
both simulations of molecular clouds and for simulations of stratified boxes. The tabulated
data required for integrating our method in hydrodynamical codes, along with a fortran
implementation of the interpolating function are publicly available here.
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A fast and robust recipe for modeling non-ideal MHD effects in star-formation simulations
