Shock Heating Due to Accretion of a Clumpy Cloud onto a Protoplanetary Disk
Shock Heating Due to Accretion of a Clumpy Cloud onto a Protoplanetary Disk
复制标题
由于块状云吸积到原行星盘上而产生的冲击加热
DOI：
10.1006/icar.1998.5947
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发表时间：
1998
期刊：
影响因子：
3.2
通讯作者：
Y. Nakagawa
中科院分区：
文献类型：
--
作者：
Kyoko K. Tanaka;Hidekazu Tanaka;K. Nakazawa;Y. Nakagawa
作为球粒形成机制的候选者，我们在局域一维气体动力学的框架下，用数值模拟方法研究了小行星轨道附近原行星盘上致密云团的吸积过程。在我们的模拟中，我们精确地考虑了控制盘温度的辐射传递过程。另一方面，我们忽略了冲击波的详细结构，因为在冲击波区域的尘埃粒子的加热是无效的。增生团块的特征在于两个参数，即，尺寸zcl和表面密度zcl，其中我们假设团块的速度等于自由落体速度。对不同的云团参数zcl和zrcl进行了数值模拟，得到了云团落在圆盘上形成激波的产生和传播的定性特征。此外，我们还发现了凝聚体吸积过程中所达到的最高温度的定量行为。最高温度以复杂的方式取决于参数（zcl和zrcl）和圆盘r d中尘埃颗粒的典型尺寸。通过数值模拟，我们找到了一组合适的参数，在这些参数下，团簇吸积导致高温阶段（~ 1500 K）。此外，基于数值模拟，我们从理论上推导出了一个简单的公式，该公式近似地给出了最高温度作为cluplant参数的函数。与观测到的代表性团块云相比，对于相同大小的代表性团块，产生陨石球粒需要大于约102至103倍的表面密度。为了证实球粒的形成是由于星团吸积的可能性，需要对星团云进行更广泛的观测和详细的理论研究。
Abstract As a candidate of mechanism of chondrule formation we have investigated the accretion of a compact clumpy cloud onto the protoplanetary disk near the asteroid orbit by means of numerical simulations in a framework of local one-dimensional gas dynamics. In our simulation, we have taken into account precisely the process of radiative transfer which governs the temperature of the disk. On the other hand, we neglected the detailed structure of the shocks because heating of dust particles in the shock regions is not effective. The accreting clump is characterized by two parameters, i.e., the size z cl and the surface density Σ cl , where we assume that the velocity of the clump is equal to the free fall velocity. For the various clumpy parameters, z cl and Σ cl , we have made numerical simulations and found the qualitative features of the generation and the propagation of the shock formed by a clumpy cloud infalling onto the disk. Furthermore, we have found the quantitative behavior of the highest temperature attained in the clumpy accretion. The highest temperature depends in a complicated manner on the parameters ( z cl and Σ cl ) and typical size of dust particles in the disk r d . By the present numerical simulations, we have found suitable sets of the parameters with which the clumpy accretion leads to the high temperature stage (≳1500 K). Furthermore, based on the numerical simulations we have theoretically derived a simple formula which gives approximately the highest temperature as a function of the clumpy parameters. In comparison with the observed representative clumpy clouds, more than about 10 2 to 10 3 times surface densities for the same size of the representative clump are needed to produce chondrules. To confirm the possibility that chondrule formation is due to the clumpy accretion, more extensive observational and detailed theoretical works on the clumpy clouds are necessary.
影响因子：
3.2
作者：
K. Miyake;Y. Nakagawa
通讯作者：
K. Miyake;Y. Nakagawa