Protoplanetary Propellers in Perturbed Accretion Disks.

在这个研究项目中，我们想要将我们的散射-扩散模型，适用于行星环中的小卫星，扩展到行星盘中正在生长的行星胚胎。尽管行星环和行星盘有很大的不同，但它们有一些共同的基本物理过程，证明了这种方法的合理性，并为这个项目提供了基础。自从90年代中期太阳系外行星的探测以来，行星形成理论得到了复兴。探测到距离中央恒星非常近的类木星行星，启动了对盘-行星相互作用和原行星相关迁移的研究。我们区分了两类正在迁移的行星：一类是导致行星空隙的行星，另一类是无法清除盘中空隙的小型原行星。这些类让人密切地想起行星环中的小卫星--比如土星S、潘和达夫尼斯创造了一个空的空隙，或者像我们的模型预测的那样，在行星环中雕刻了螺旋桨般的结构。事实上，卡西尼号航天器上的相机捕捉到了数百个由大小为50-150米的小卫星造成的螺旋桨！此外，还发现了一个指向一个千米大小的小卫星的非常大的螺旋桨，它随机地迁移。两个圆盘中明显的相似之处引发了这样的问题：无间隙开放的行星是否会在行星前圆盘中诱导出类似螺旋桨的结构？在什么情况下？这些行星是否引起了垂直盘状层结的明显变化？什么过程可以破坏螺旋桨状结构的对称性，从而导致行星迁移？吸积的行星胚胎对周围的盘状结构有什么影响？最后，土星S环中迁移的小卫星的事实为行星环是宇宙盘的自然动力学实验室提供了终极证据，也支持了扩展的散射-扩散模型对行星形成/迁移的可能重要性。

In this research project we want to extend our scattering-diffusion model, suitable for moonlets in planetary rings, to growing planetary embryos in preplanetary disks. Despite their large differences planetary rings and preplanetary disks share a few essential physical processes justifying this approach and providing the base for this project.Since the detection of extrasolar planets in the middle of the 90ties theories of planet formation have gained a renaissance. The detection of Jovian-like planets very close to the central star has initiated investigations of disk-planet interactions and related migration of protoplanets. Two classes of migrating planets are distinguished: laige gap-inducing planets, and alternatively, small protoplanets unable to clear a gap in the disk.These classes remind closely of moonlets in planetary rings - such as Saturn s Pan and Daphnis creating an empty gap or those carving propeller-like structures in planetary rings as predicted by our models. And indeed, the cameras on the Cassini spacecraft caught a few hundred propellers caused by moonlets with sizes of 50 ... 150 meters! Moreover, a very large propeller pointing to a kilometer-sized moonlet has been found which migrates stochastically.The obvious analogies in both disks provoke the questions: Do non-gap opening planets induce propeller-like structures in preplanetary disks? Under which conditions? Do these planets cause observable modifications of the vertical disk-stratification? What processes can break the symmetry of the propeller-like structures to cause planetary migration? What is the effect of an accreting planetary embryo on the surrounding disk-structure?And finally, the very fact of a migrating moonlet in Saturn s rings provides an ultimate proof for planetary rings being a natural dynamical lab for cosmic disks and also supports the possible importance of an extended scattering-diffusion model for planet formation/migration.