Gold Alignment and Internal Dissipation
Gold Alignment and Internal Dissipation
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黄金对准和内部耗散
DOI：
10.1086/304201
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
A. Lazarian
中科院分区：
文献类型：
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作者：
A. Lazarian
对于长圆形和扁圆形颗粒，其温度与颗粒动能除以玻尔兹曼常数k相当，得到了机械取向的量度。对于这种颗粒，角动量J与最大惯量轴a的排列只是局部的，与Lazarian和Roberge，Hanany和Messinger在完全排列的假设下得到的结果相比，这实质上改变了机械排列。我们还描述了当Barnett耗散被抑制时的Gold取向，并导出了取向度量与颗粒非球度参数和气粒漂移方向之间的关系的解析表达式。这个解给出了对齐度量的下限，而上限则是由拉扎里安提出的方法给出的。利用Lazarian和Roberge最近关于不完全内驰豫的研究结果，我们找到了整个颗粒转动能与Kts之比范围内的取向度量，其中ts是颗粒温度。为了描述适度超音速漂移的对准，我们提出了一种分析方法，该方法与Roberge，Hanany和Messinger的直接数值模拟结果具有很好的一致性。我们还扩展了我们的方法来解释Gold和Davis-Greenstein机制的同时作用。
The measures of mechanical alignment are obtained for both prolate and oblate grains whose temperatures are comparable to the grain kinetic energy divided by k, the Boltzmann constant. For such grains, the alignment of angular momentum, J, with the axis of maximal inertia, a, is only partial, which substantially alters the mechanical alignment as compared with the results obtained by Lazarian and Roberge, Hanany, & Messinger under the assumption of perfect alignment. We also describe Gold alignment when the Barnett dissipation is suppressed and derive an analytical expression that relates the measure of alignment to the parameters of grain nonsphericity and the direction of the gas-grain drift. This solution provides the lower limit for the measure of alignment, while the upper limit is given by the method derived by Lazarian. Using the results of a recent study of incomplete internal relaxation by Lazarian & Roberge, we find measures of alignment for the whole range of ratios of grain rotational energy to kTs, where Ts is the grain temperature. To describe alignment for mildly supersonic drifts, we suggest an analytical approach that provides good correspondence with the results of direct numerical simulations by Roberge, Hanany, & Messinger. We also extend our approach to account for simultaneous action of the Gold and Davis-Greenstein mechanisms.