Unlocking planetesimal magnetic field histories: A refined, versatile model for thermal evolution and dynamo generation

IF 2.5 2区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS
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Abstract

The thermal and magnetic histories of planetesimals provide unique insights into the formation and evolution of Earth’s building blocks. These histories can be gleaned from meteorites by using numerical models to translate measured properties into planetesimal behaviour. In this paper, we present a new 1D planetesimal thermal evolution and dynamo generation model. This magnetic field generation model is the first of a differentiated, mantled planetesimal that includes both mantle convection and sub-eutectic core solidification. We have improved fundamental aspects of mantle heat transport by including a more detailed viscosity model and stagnant lid convection parametrisations consistent with internal heating. We have also added radiogenic heating from 60Fe in the metallic Fe-FeS core. Additionally, we implement a combined thermal and compositional buoyancy flux, as well as the latest magnetic field scaling laws to predict magnetic field strengths during the planetesimal’s thermal evolution until core solidification is complete. We illustrate the consequences of our model changes with an example run for a 500 km radius planetesimal. These effects include more rapid erosion of core thermal stratification and longer duration of mantle convection compared to previous studies. The additional buoyancy from core solidification has a marginal effect on dynamo strength, but for some initial core sulfur contents it can prevent cessation of the dynamo when mantle convection ends. Our model can be used to investigate the effects of individual parameters on dynamo generation and constrain properties of specific meteorite parent bodies. Combined, these updates mean this model can predict the most reliable and complete magnetic field history for a planetesimal to date, so is a valuable tool for deciphering planetesimal behaviour from meteorite properties.
揭开行星磁场的历史:热演化和动力生成的精炼、多功能模型
行星碎块的热历史和磁性历史为了解地球组成元素的形成和演变提供了独特的视角。通过使用数值模型将测量到的特性转化为行星的行为,可以从陨石中收集到这些历史。在本文中,我们提出了一个新的一维行星热演化和动力生成模型。这个磁场生成模型是第一个包含地幔对流和亚共晶内核凝固的分化幔状行星模型。我们改进了地幔热传输的基本方面,包括一个更详细的粘度模型和与内部加热一致的停滞盖对流参数。我们还增加了金属铁-铁-硒内核中 60Fe 的辐射加热。此外,我们还采用了热浮力通量和成分浮力通量的组合,以及最新的磁场缩放定律来预测行星热演化过程中的磁场强度,直到内核凝固完成。我们以一个半径为 500 公里的行星为例,说明了模型变化的后果。与以前的研究相比,这些影响包括内核热分层侵蚀更快,地幔对流持续时间更长。内核凝固产生的额外浮力对动力强度的影响微乎其微,但对于某些初始内核硫含量,它可以防止地幔对流结束时动力停止。我们的模型可用于研究单个参数对动力生成的影响,并约束特定陨石母体的属性。这些更新意味着这个模型可以预测迄今为止最可靠和最完整的行星磁场历史,因此是一个从陨石特性来解读行星行为的宝贵工具。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Icarus
Icarus 地学天文-天文与天体物理
CiteScore
6.30
自引率
18.80%
发文量
356
审稿时长
2-4 weeks
期刊介绍: Icarus is devoted to the publication of original contributions in the field of Solar System studies. Manuscripts reporting the results of new research - observational, experimental, or theoretical - concerning the astronomy, geology, meteorology, physics, chemistry, biology, and other scientific aspects of our Solar System or extrasolar systems are welcome. The journal generally does not publish papers devoted exclusively to the Sun, the Earth, celestial mechanics, meteoritics, or astrophysics. Icarus does not publish papers that provide "improved" versions of Bode''s law, or other numerical relations, without a sound physical basis. Icarus does not publish meeting announcements or general notices. Reviews, historical papers, and manuscripts describing spacecraft instrumentation may be considered, but only with prior approval of the editor. An entire issue of the journal is occasionally devoted to a single subject, usually arising from a conference on the same topic. The language of publication is English. American or British usage is accepted, but not a mixture of these.
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