GRAVOTURBULENT PLANETESIMAL FORMATION: THE POSITIVE EFFECT OF LONG-LIVED ZONAL FLOWS
GRAVOTURBULENT PLANETESIMAL FORMATION: THE POSITIVE EFFECT OF LONG-LIVED ZONAL FLOWS
复制标题
重力湍流星子形成：长寿命纬向流的积极影响
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
A. Johansen
中科院分区：
文献类型：
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作者：
Karsten Dittrich;H. Klahr;A. Johansen
最近的数值模拟表明，在原行星盘中存在长寿命的轴对称次和超开普勒流。这些纬向流被发现在本地以及全球模拟磁盘不稳定的磁旋转不稳定性。本文涵盖了我们的研究的强度和寿命的纬向流和由此产生的长寿命的气体过密度和欠密度的函数的方位角和径向尺寸的本地剪切盒。我们进一步研究尘埃粒子浓度没有反馈的气体和没有自重力。随着模拟箱径向尺寸的增大，纬向流的强度和寿命增大，而随着模拟箱方位角尺寸的增大，纬向流的强度和寿命减小。我们的模拟支持早期的结果，纬向流有一个自然的径向长度尺度的5 - 7气体压力刻度的高度。这是第一个研究，结合三维磁流体模拟的纬向流和尘埃颗粒的感觉气体压力。压力凸起非常有效地捕获St = 1的颗粒。我们发现，St = 0.1的粒子（如果在最小质量的太阳星云中为5 Au，则尺寸为几厘米）达到比最初高出一百倍的密度。这为St = 0.1和尘气比为0.01的粒子或St = 0.5和尘气比为10 − 4的粒子仍然达到可能触发流动不稳定性的密度打开了通道，从而形成了微行星的重力湍流。
Recent numerical simulations have shown long-lived axisymmetric sub- and super-Keplerian flows in protoplanetary disks. These zonal flows are found in local as well as global simulations of disks unstable to the magnetorotational instability. This paper covers our study of the strength and lifetime of zonal flows and the resulting long-lived gas over- and underdensities as functions of the azimuthal and radial size of the local shearing box. We further investigate dust particle concentrations without feedback on the gas and without self-gravity. The strength and lifetime of zonal flows increase with the radial extent of the simulation box, but decrease with the azimuthal box size. Our simulations support earlier results that zonal flows have a natural radial length scale of 5–7 gas pressure scale heights. This is the first study that combines three-dimensional MHD simulations of zonal flows and dust particles feeling the gas pressure. The pressure bumps trap particles with St = 1 very efficiently. We show that St = 0.1 particles (of some centimeters in size if at 5 AU in a minimum mass solar nebula) reach a hundred-fold higher density than initially. This opens the path for particles of St = 0.1 and dust-to-gas ratio of 0.01 or for particles of St ⩾ 0.5 and dust-to-gas ratio 10−4 to still reach densities that potentially trigger the streaming instability and thus gravoturbulent formation of planetesimals.