木卫三地下海洋中的对流流动：对感应磁场和地形的影响

IF 3 2区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

Icarus Pub Date : 2025-09-13 DOI:10.1016/j.icarus.2025.116807

Jakub Kvorka, Ondřej Čadek, Libor Šachl, Jakub Velímský

{"title":"木卫三地下海洋中的对流流动：对感应磁场和地形的影响","authors":"Jakub Kvorka, Ondřej Čadek, Libor Šachl, Jakub Velímský","doi":"10.1016/j.icarus.2025.116807","DOIUrl":null,"url":null,"abstract":"<div><div>Subsurface oceans of icy moons are inaccessible to direct observation and numerical modeling is currently the only way to study the dynamics of these systems. Here, we present the first comprehensive study of Ganymede’s ocean based on the numerical simulations of thermal convection in a rotating spherical shell, and discuss the implications of the flow circulation for Ganymede’s long-wavelength topography and induced magnetic field. In order to determine the structure of the flow in Ganymede’s ocean, we have performed 128 numerical simulations, varying all relevant control parameters (<span><math><mrow><mi>R</mi><mi>a</mi></mrow></math></span>, <span><math><mrow><mi>E</mi><mi>k</mi></mrow></math></span>, <span><math><mrow><mi>P</mi><mi>r</mi></mrow></math></span>) by at least one order of magnitude. Based on this data set, we predict that the ocean circulation is characterized by a retrograde equatorial jet, meridional circulation cells at low latitudes and narrow upwellings and downwellings in the polar regions. The mean speed of the ocean flow ranges from a few cm/s for a thin (<span><math><mrow><mo><</mo><mspace></mspace><mn>100</mn></mrow></math></span> km) ocean to 0.8m/s for a 500km thick ocean. The time-averaged heat flux from the ocean varies with the latitude reaching the maximum at the poles and the minimum at mid-latitudes. Assuming that the heat transfer in the ice shell is dominated by conduction, we determine Ganymede’s long-wavelength topography generated by the uneven heat flux from the ocean. We predict that Ganymede’s polar regions are flat or even elevated and the global topographic pattern is dominated by an equatorial depression and elevations at mid-latitudes. Preliminary calculations of the magnetic field, induced by the flow of the salty ocean in the presence of Ganymede’s internal magnetic field, predict sufficiently large amplitudes to allow their detection by the Juice and Europa Clipper spacecrafts. We demonstrate that the pattern of the flow-induced magnetic field strongly depends on the geometry of ocean circulation, suggesting that accurate magnetic measurements can provide constraints on the dynamics of Ganymede’s ocean.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"444 ","pages":"Article 116807"},"PeriodicalIF":3.0000,"publicationDate":"2025-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Convective flow in Ganymede’s subsurface ocean: Implications for the induced magnetic field and topography\",\"authors\":\"Jakub Kvorka, Ondřej Čadek, Libor Šachl, Jakub Velímský\",\"doi\":\"10.1016/j.icarus.2025.116807\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>Subsurface oceans of icy moons are inaccessible to direct observation and numerical modeling is currently the only way to study the dynamics of these systems. Here, we present the first comprehensive study of Ganymede’s ocean based on the numerical simulations of thermal convection in a rotating spherical shell, and discuss the implications of the flow circulation for Ganymede’s long-wavelength topography and induced magnetic field. In order to determine the structure of the flow in Ganymede’s ocean, we have performed 128 numerical simulations, varying all relevant control parameters (<span><math><mrow><mi>R</mi><mi>a</mi></mrow></math></span>, <span><math><mrow><mi>E</mi><mi>k</mi></mrow></math></span>, <span><math><mrow><mi>P</mi><mi>r</mi></mrow></math></span>) by at least one order of magnitude. Based on this data set, we predict that the ocean circulation is characterized by a retrograde equatorial jet, meridional circulation cells at low latitudes and narrow upwellings and downwellings in the polar regions. The mean speed of the ocean flow ranges from a few cm/s for a thin (<span><math><mrow><mo><</mo><mspace></mspace><mn>100</mn></mrow></math></span> km) ocean to 0.8m/s for a 500km thick ocean. The time-averaged heat flux from the ocean varies with the latitude reaching the maximum at the poles and the minimum at mid-latitudes. Assuming that the heat transfer in the ice shell is dominated by conduction, we determine Ganymede’s long-wavelength topography generated by the uneven heat flux from the ocean. We predict that Ganymede’s polar regions are flat or even elevated and the global topographic pattern is dominated by an equatorial depression and elevations at mid-latitudes. Preliminary calculations of the magnetic field, induced by the flow of the salty ocean in the presence of Ganymede’s internal magnetic field, predict sufficiently large amplitudes to allow their detection by the Juice and Europa Clipper spacecrafts. We demonstrate that the pattern of the flow-induced magnetic field strongly depends on the geometry of ocean circulation, suggesting that accurate magnetic measurements can provide constraints on the dynamics of Ganymede’s ocean.</div></div>\",\"PeriodicalId\":13199,\"journal\":{\"name\":\"Icarus\",\"volume\":\"444 \",\"pages\":\"Article 116807\"},\"PeriodicalIF\":3.0000,\"publicationDate\":\"2025-09-13\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Icarus\",\"FirstCategoryId\":\"101\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0019103525003550\",\"RegionNum\":2,\"RegionCategory\":\"物理与天体物理\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"ASTRONOMY & ASTROPHYSICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Icarus","FirstCategoryId":"101","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0019103525003550","RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ASTRONOMY & ASTROPHYSICS","Score":null,"Total":0}

引用次数: 0

摘要

冰冻卫星的地下海洋是无法直接观测的，数值模拟是目前研究这些系统动力学的唯一方法。本文首次对木卫三海洋进行了基于旋转球壳热对流数值模拟的综合研究，并讨论了流动循环对木卫三长波形貌和感应磁场的影响。为了确定木卫三海洋的流动结构，我们进行了128次数值模拟，将所有相关的控制参数（Ra, Ek, Pr）至少改变一个数量级。在此基础上，我们预测海洋环流的特点是赤道急流的逆行，低纬度的经向环流单元，极地地区的狭窄上升流和下降流。海洋流动的平均速度从薄（100公里）海洋的几厘米/秒到500公里厚海洋的0.8米/秒不等。来自海洋的时间平均热通量随纬度变化，在两极达到最大值，在中纬度达到最小值。假设冰壳内的热传递以传导为主，我们确定了木卫三的长波长地形是由来自海洋的不均匀热通量产生的。我们预测木卫三的极地地区是平坦的，甚至是高的，全球地形模式由赤道洼地和中纬度地区的高地主导。在木卫三内部磁场存在的情况下，由含盐海洋的流动引起的磁场的初步计算，预测了足够大的振幅，可以让Juice和Europa Clipper航天器探测到。我们证明了流诱导磁场的模式强烈依赖于海洋环流的几何形状，这表明精确的磁场测量可以为木卫三海洋的动力学提供约束。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

查看原文本刊更多论文

Convective flow in Ganymede’s subsurface ocean: Implications for the induced magnetic field and topography

Subsurface oceans of icy moons are inaccessible to direct observation and numerical modeling is currently the only way to study the dynamics of these systems. Here, we present the first comprehensive study of Ganymede’s ocean based on the numerical simulations of thermal convection in a rotating spherical shell, and discuss the implications of the flow circulation for Ganymede’s long-wavelength topography and induced magnetic field. In order to determine the structure of the flow in Ganymede’s ocean, we have performed 128 numerical simulations, varying all relevant control parameters (

R a

E k

P r

) by at least one order of magnitude. Based on this data set, we predict that the ocean circulation is characterized by a retrograde equatorial jet, meridional circulation cells at low latitudes and narrow upwellings and downwellings in the polar regions. The mean speed of the ocean flow ranges from a few cm/s for a thin (

< 100

km) ocean to 0.8 m/s for a 500 km thick ocean. The time-averaged heat flux from the ocean varies with the latitude reaching the maximum at the poles and the minimum at mid-latitudes. Assuming that the heat transfer in the ice shell is dominated by conduction, we determine Ganymede’s long-wavelength topography generated by the uneven heat flux from the ocean. We predict that Ganymede’s polar regions are flat or even elevated and the global topographic pattern is dominated by an equatorial depression and elevations at mid-latitudes. Preliminary calculations of the magnetic field, induced by the flow of the salty ocean in the presence of Ganymede’s internal magnetic field, predict sufficiently large amplitudes to allow their detection by the Juice and Europa Clipper spacecrafts. We demonstrate that the pattern of the flow-induced magnetic field strongly depends on the geometry of ocean circulation, suggesting that accurate magnetic measurements can provide constraints on the dynamics of Ganymede’s ocean.

求助全文

通过发布文献求助，成功后即可免费获取论文全文。去求助

来源期刊

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.