Dependence of Hall coefficient on grain size and cosmic ray rate and implication for circumstellar disc formation
Dependence of Hall coefficient on grain size and cosmic ray rate and implication for circumstellar disc formation
复制标题
霍尔系数对晶粒尺寸和宇宙射线速率的依赖性及其对星周盘形成的影响
DOI：
10.1093/mnras/sty3524
复制
发表时间：
2019
影响因子：
4.8
通讯作者：
Masahiro N.
中科院分区：
文献类型：
--
作者：
Koga;Shunta; Tsukamoto;Yusuke; Okuzumi;Satoshi; Machida;Masahiro N.
霍尔效应在恒星形成中起着重要作用，因为它会引起坠落包层的旋转，进而影响星周盘的形成和演化。霍尔效应的重要性随霍尔系数的不同而变化，而该系数由带电物质的丰度分数决定。这些丰度值主要基于尘埃颗粒的大小和数量以及宇宙射线强度，它们分别吸收和产生带电物质。因此，霍尔系数随尘埃颗粒的性质和宇宙射线速率（或电离源）而变化。在这项研究中，我们使用简化的化学网络模型探索霍尔系数对晶粒尺寸和宇宙射线电离率的依赖性。接下来，使用分析模型，我们估计了仅由霍尔效应引起的星周盘的典型尺寸。结果表明，圆盘在主要吸积阶段生长至~3-100 au的尺寸，实际尺寸取决于参数。这些发现表明霍尔效应极大地影响星周盘的形成，特别是在尘埃颗粒具有典型尺寸的情况下。
The Hall effect plays a significant role in star formation, because it induces rotation in the infalling envelope, which in turn affects the formation and evolution of the circumstellar disc. The importance of the Hall effect varies with the Hall coefficient, and this coefficient is determined by the fractional abundances of charged species. These abundance values are primarily based on the size and quantity of dust grains as well as the cosmic ray intensity, which, respectively, absorb and create charged species. Thus, the Hall coefficient varies with both the properties of dust grains and the cosmic ray rate (or ionization source). In this study, we explore the dependence of the Hall coefficient on the grain size and cosmic ray ionization rate using a simplified chemical network model. Following this, using an analytic model, we estimate the typical size of a circumstellar disc induced solely by the Hall effect. The results show that the disc grows during the main accretion phase to a size of ∼3–100 au, with the actual size depending on the parameters. These findings suggest that the Hall effect greatly affects circumstellar disc formation, especially in the case that the dust grains have a typical size of.