Self-sustained Ionization and Vanishing Dead Zones in Protoplanetary Disks
Self-sustained Ionization and Vanishing Dead Zones in Protoplanetary Disks
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DOI：
10.1086/432796
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发表时间：
2005-06
期刊：
影响因子：
--
通讯作者：
S. Inutsuka;T. Sano
中科院分区：
文献类型：
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作者：
S. Inutsuka;T. Sano
我们分析了磁流体动力学湍流原行星盘的电离状态，并提出了一种维持电离的新机制。首先，我们表明，在具有尘埃颗粒的典型原行星盘中，在由磁旋转不稳定性驱动的准稳态湍流中，能量耗散量应足以提供激活磁旋转不稳定性所需的电离能。其次，我们表明，在带有尘埃颗粒的圆盘中，在弱电离气体中构成电流的高能电子可以提供碰撞电离，具体取决于磁旋转湍流的实际饱和状态。另一方面，我们表明，在尘埃颗粒影响减弱的原行星盘中，湍流运动可以使电离程度均匀化，即使在没有其他电离过程的情况下，也可以激活磁旋转不稳定性。这封信中的结果表明，原行星盘中的大多数区域仍然具有磁性活跃，因此我们需要改变行星形成的理论模型。
We analyze the ionization state of the magnetohydrodynamically turbulent protoplanetary disks and propose a new mechanism of sustaining ionization. First, we show that in the quasi-steady state of turbulence driven by magnetorotational instability in a typical protoplanetary disk with dust grains, the amount of energy dissipation should be sufficient for providing the ionization energy that is required for activating magnetorotational instability. Second, we show that in the disk with dust grains the energetic electrons that compose electric currents in weakly ionized gas can provide collisional ionization, depending on the actual saturation state of magnetorotational turbulence. On the other hand, we show that in the protoplanetary disks with the reduced effect of dust grains, the turbulent motion can homogenize the ionization degree, which can activate magnetorotational instability even in the absence of other ionization processes. The results in this Letter indicate that most of the regions in protoplanetary disks remain magnetically active, and we thus require a change in the theoretical modeling of planet formation.