arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2108.01604astro-ph.EP
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将天王星的温度分布与风致磁场联系起来

Linking Uranus' temperature profile to wind-induced magnetic fields

Deniz Soyuer, Ravit Helled

摘要:

天王星的低光度仍然是一个令人困惑的现象,并对行星内部的热量和成分梯度有关键的影响。最近的研究表明,行星挥发物在冰巨星存在的条件下变得具有离子导电性。随着深度的增加,快速增长的电导率将把纬向流耦合到行星的背景磁场,通过$ω$效应诱导极向和环向场扰动$\mathbf{B}^ω = \mathbf{B}^ω_P + \mathbf{B}^ω_T$。环形扰动$\mathbf{B}^ω_T$预计将向下扩散,并通过$α$效应的湍流对流产生极向场$\mathbf{B}^α_P$,其强度与$ω$效应的强度相当; $\mathbf{B}^ω_P$。为了估计文献中各种天王星模型的极向场扰动的强度,我们假设离子导电H $_2$ -He-H $_2$ O内部的欧姆耗散约束的基础上产生风衰减配置文件。由于热天王星模型外部区域的金属丰度较高,纬向风需要衰减到天王星外部1%区域表面值的$\sim$ 0.1%,才能在欧姆框架中接受衰变解。我们的估计表明,在最极端的情况下,较冷的天王星模型可能具有高达背景磁场的$\mathcal{O}(0.1)$的极向场扰动。可能存在的极向场扰动与天王星纬向流的空间相关性可以用来约束天王星的内部结构,并提供了进一步的情况下,$\textit{in situ}$探测天王星。

英文摘要:

The low luminosity of Uranus is still a puzzling phenomenon and has key implications for the thermal and compositional gradients within the planet. Recent studies have shown that planetary volatiles become ionically conducting under conditions that are present in the ice giants. Rapidly growing electrical conductivity with increasing depth would couple zonal flows to the background magnetic field in the planets, inducing poloidal and toroidal field perturbations $\mathbf{B}^ω = \mathbf{B}^ω_P + \mathbf{B}^ω_T$ via the $ω$-effect. Toroidal perturbations $\mathbf{B}^ω_T$ are expected to diffuse downwards and produce poloidal fields $\mathbf{B}^α_P$ through turbulent convection via the $α$-effect, comparable in strength to those of the $ω$-effect; $\mathbf{B}^ω_P$. To estimate the strength of poloidal field perturbations for various Uranus models in the literature, we generate wind decay profiles based on Ohmic dissipation constraints assuming an ionically conducting H$_2$-He-H$_2$O interior. Due to the higher metallicities in outer regions of hot Uranus models, zonal winds need to decay to $\sim$0.1% of their surface values in the outer 1% of Uranus to admit decay solutions in the Ohmic framework. Our estimates suggest that colder Uranus models could potentially have poloidal field perturbations that reach up to $\mathcal{O}(0.1)$ of the background magnetic field in the most extreme case. The possible existence of poloidal field perturbations spatially correlated with Uranus' zonal flows could be used to constrain Uranus' interior structure, and presents a further case for the $\textit{in situ}$ exploration of Uranus.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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