We investigate and discuss protostellar discs in terms of where the various non-ideal magnetohydrodynamics (MHD) processes are important. We find that the traditional picture of a magnetised disc (where Ohmic resistivity is dominant near the mid-plane, surrounded by a region dominated by the Hall effect, with the remainder of the disc dominated by ambipolar diffusion) is a great oversimplification. In simple parameterised discs, we find that the Hall effect is typically the dominant term throughout the majority of the disc. More importantly, we find that in much of our parameterised discs, at least two non-ideal processes have coefficients within a factor of 10 of one another, indicating that both are important and that naming a dominant term underplays the importance of the other terms. Discs that were self-consistently formed in our previous studies are also dominated by the Hall effect, and the ratio of ambipolar diffusion and Hall coefficients is typically less than 10, suggesting that both terms are equally important and listing a dominant term is misleading. These conclusions become more robust once the magnetic field geometry is taken into account. In agreement with the literature we review, we conclude that non-ideal MHD processes are important for the formation and evolution of protostellar discs. Ignoring any of the non-ideal processes, especially ambipolar diffusion and the Hall effect, yields an incorrect description of disc evolution.

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我们是否需要非理想的 MHD 来模拟原恒星盘？

我们根据各种非理想磁流体动力学 (MHD) 过程的重要性来研究和讨论原恒星盘。我们发现磁化圆盘的传统图片（其中欧姆电阻率在中平面附近占主导地位，周围环绕着霍尔效应主导的区域，圆盘的其余部分由双极扩散主导）是一个极大的过度简化。在简单的参数化圆盘中，我们发现霍尔效应通常是整个圆盘大部分的主要项。更重要的是，我们发现在我们的大部分参数化圆盘中，至少有两个非理想过程的系数在彼此的 10 倍以内，这表明两者都很重要，并且命名一个主导术语会低估其他术语的重要性。在我们之前的研究中自洽形成的圆盘也受霍尔效应的支配，双极扩散和霍尔系数的比率通常小于 10，这表明这两个术语同样重要，列出主导术语具有误导性。一旦考虑到磁场几何形状，这些结论就会变得更加可靠。与我们回顾的文献一致，我们得出结论，非理想的 MHD 过程对于原恒星盘的形成和演化很重要。忽略任何非理想过程，尤其是双极扩散和霍尔效应，会产生对光盘演化的错误描述。暗示这两个术语同等重要并且列出主要术语是误导性的。一旦考虑到磁场几何形状，这些结论就会变得更加可靠。与我们回顾的文献一致，我们得出结论，非理想的 MHD 过程对于原恒星盘的形成和演化很重要。忽略任何非理想过程，尤其是双极扩散和霍尔效应，会产生对光盘演化的错误描述。暗示这两个术语同等重要并且列出主要术语是误导性的。一旦考虑到磁场几何形状，这些结论就会变得更加可靠。与我们回顾的文献一致，我们得出结论，非理想的 MHD 过程对于原恒星盘的形成和演化很重要。忽略任何非理想过程，尤其是双极扩散和霍尔效应，会产生对光盘演化的错误描述。