标题： 彗星尘埃尾中条纹的形成通过升华驱动的类似YORP效应 显示英文标题

标题： The Formation of Striae within Cometary Dust Tails by a Sublimation-Driven YORP-like Effect

摘要： 升华的气体分子以与光子相同的方式从冰质天体的表面散射。这意味着对于每一个由光子驱动的体力，应该有一个由升华驱动的类似效应影响冰质天体。太阳系中形状不对称天体表面发出的热光子产生净力矩，随着时间的推移改变这些天体的自转速率。这种力矩的长期平均称为YORP效应。在这里，我们提出YORP效应的一个由升华驱动的类似效应（SYORP），其中从冰质天体表面升华的气体分子也会在天体上产生净力矩。然而，升华的分子以比热光子高约10^4-10^5倍的速率将动量带走，导致更大的天体力矩。虽然以前对升华力矩的研究集中在木星族彗星核表面上高度局部化的发射源，但SYORP适用于整个天体上的非局部化发射，这可能主导小冰质碎片和动态年轻的彗星上的升华驱动力矩，并且因此可以在没有对其表面进行高分辨率航天器观测的情况下应用。相反，我们重新利用YORP效应的方程来考虑由升华驱动的力矩。我们展示了由SYORP驱动的机制如何最好地匹配彗尾的太阳取向条纹（条纹）的观测结果，其形成机制几十年来一直是个谜。SYORP效应解释了为什么对于近日点小于0.6天文单位的彗星，条纹被观测到在近日点附近和大约1天文单位处的太阳附近，解决了长期以来将足够多的物质带入彗星尾部以形成可见条纹的问题。我们表明SYORP可以形成与韦斯特彗星相似的条纹，并产生一个指数为-1.4（-1.1-2）的母块大小频率分布。 显示英文摘要

摘要： Sublimating gas molecules scatter off of the surface of an icy body in the same manner as photons. This means that for every photon-driven body force, there should be a sublimation-driven analogue that affects icy bodies. Thermal photons emitted from the surfaces of asymmetrically shaped bodies in the Solar System generate net torques that change the spin rates of these bodies over time. The long-term averaging of this torque is called the YORP effect. Here we propose a sublimation-driven analogue to the YORP effect (SYORP), in which sublimating gas molecules emitted from the surfaces of icy bodies also generate net torques on the bodies. However, sublimating molecules carry momentum away from the body at a rate ~10^4-10^5 greater than thermal photons, resulting in much greater body torques. While previous studies of sublimative torques focused on emissions from highly localized sources on the surfaces of Jupiter Family Comet nuclei, SYORP applies to non-localized emissions across the entire body, which likely dominates sublimation-drive torques on small icy chunks and Dynamically Young Comets, and can therefore be applied without high-resolution spacecraft observations of their surfaces. Instead, we repurpose the equations of the YORP effect to account for sublimation-driven torques. We show how an SYORP-driven mechanism best matches observations of the Sun-oriented lineaments (striae) of comet tails, whose formation mechanism has remained enigmatic for decades. The SYORP effect explains why striae are observed between near-perihelion and ~1 AU from the Sun for comets with perihelia less than 0.6 AU, and solves longstanding problems with moving enough material into the cometary tail to form visible striae. We show that SYORP can form striae that match those of Comet West, and produce a power-law size frequency distribution of their parent chunks with an index of -1.4 (-1.1- 2).