Global simulations of protoplanetary disks with net magnetic flux I. Non-ideal MHD case
Global simulations of protoplanetary disks with net magnetic flux I. Non-ideal MHD case
复制标题
DOI：
10.1051/0004-6361/201630056
复制
发表时间：
2017-04-01
影响因子：
6.5
通讯作者：
Ferreira, Jonathan
中科院分区：
文献类型：
--
作者：
Bethune, William;Lesur, Geoffroy;Ferreira, Jonathan
上下文原行星盘的行星形成区域是冷的、致密的，因此电离很弱。由于这个原因，磁流体动力学（MHD）湍流被认为是大多数情况下不存在的，并找到另一种机制来解释气体吸积。有人提出，从电离盘表面发射的磁化风可以在大尺度磁场存在的情况下驱动吸积。效率和这些表面风对磁盘结构的影响仍然非常不确定。我们提出了第一个全球模拟的弱电离磁盘，表现出大规模的磁化风。我们还研究了自组织的影响，这是以前只证明了在非分层模型。我们用PLUTO程序对分层圆盘进行了数值模拟。我们计算的电离分数动态，并占所有三个非理想的MHD效应：欧姆和双极扩散，霍尔漂移。简化的加热和冷却，由于非热辐射也被考虑在磁盘大气。我们发现，磁盘可以吸积或不吸积，这取决于大尺度磁场的配置。磁热风，驱动的磁加速和加热的大气，在吸积的情况下得到的。在某些情况下，这些风是不对称的，主要在圆盘的一侧喷射。风的质量损失率主要取决于磁盘中平面的磁压力与热压力的平均比率。非吸积的情况下，其特征在于由一个涡卷环流，吸积层在磁盘表面和中平面的decretion。最后，我们观察到自组织，导致轴对称环的密度和相关的压力“颠簸”。的基本机制及其对可观察到的结构的影响进行了讨论。
Context. The planet-forming region of protoplanetary disks is cold, dense, and therefore weakly ionized. For this reason, magnetohydrodynamic (MHD) turbulence is thought to be mostly absent, and another mechanism has to be found to explain gas accretion. It has been proposed that magnetized winds, launched from the ionized disk surface, could drive accretion in the presence of a large-scale magnetic field.Aims. The efficiency and the impact of these surface winds on the disk structure is still highly uncertain. We present the first global simulations of a weakly ionized disk that exhibits large-scale magnetized winds. We also study the impact of self-organization, which was previously demonstrated only in non-stratified models.Methods. We perform numerical simulations of stratified disks with the PLUTO code. We compute the ionization fraction dynamically, and account for all three non-ideal MHD effects: ohmic and ambipolar diffusions, and the Hall drift. Simplified heating and cooling due to non-thermal radiation is also taken into account in the disk atmosphere.Results. We find that disks can be accreting or not, depending on the configuration of the large-scale magnetic field. Magnetothermal winds, driven both by magnetic acceleration and heating of the atmosphere, are obtained in the accreting case. In some cases, these winds are asymmetric, ejecting predominantly on one side of the disk. The wind mass loss rate depends primarily on the average ratio of magnetic to thermal pressure in the disk midplane. The non-accreting case is characterized by a meridional circulation, with accretion layers at the disk surface and decretion in the midplane. Finally, we observe self-organization, resulting in axisymmetric rings of density and associated pressure "bumps". The underlying mechanism and its impact on observable structures are discussed.