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DOI | 10.1073/pnas.1717454115 |
Geomagnetic polar minima do not arise from steady meridional circulation | |
Cao, Hao1,2; Yadav, Rakesh K.1; Aurnou, Jonathan M.3 | |
2018-10-30 | |
发表期刊 | PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA |
ISSN | 0027-8424 |
出版年 | 2018 |
卷号 | 115期号:44页码:11186-11191 |
文章类型 | Article |
语种 | 英语 |
国家 | USA |
英文摘要 | Observations of the Earth's magnetic field have revealed locally pronounced field minima near each pole at the core-mantle boundary (CMB). The existence of the polar magnetic minima has long been attributed to the supposed large-scale overturning circulation of molten metal in the outer core: Fluid upwells within the inner core tangent cylinder toward the poles and then diverges toward lower latitudes when it reaches the CMB, where Coriolis effects sweep the fluid into anticyclonic vortical flows. The diverging near-surface meridional circulation is believed to advectively draw magnetic flux away from the poles, resulting in the low intensity or even reversed polar magnetic fields. However, the interconnections between polar magnetic minima and meridional circulations have not to date been ascertained quantitatively. Here, we quantify the magnetic effects of steady, axisymmetric meridional circulation via numerically solving the axisymmetric magnetohydrodynamic equations for Earth's outer core under the magnetostrophic approximation. Extrapolated to core conditions, our results show that the change in polar magnetic field resulting from steady, large-scale meridional circulations in Earth's outer core is less than 3% of the background field, significantly smaller than the similar to 100% polar magnetic minima observed at the CMB. This suggests that the geomagnetic polar minima cannot be produced solely by axisymmetric, steady meridional circulations and must depend upon additional tangent cylinder dynamics, likely including nonaxisymmetric, time-varying processes. |
英文关键词 | geodynamo polar magnetic minima polar vortex gyroscopic pumping flow magnetic field interactions |
领域 | 地球科学 ; 气候变化 ; 资源环境 |
收录类别 | SCI-E |
WOS记录号 | WOS:000448713200041 |
WOS关键词 | EARTHS INNER-CORE ; PLANETARY MAGNETIC-FIELDS ; SPHERICAL-SHELL ; ROTATING FLUID ; GEODYNAMO ; DYNAMO ; CONVECTION ; MODELS ; DRIVEN ; EVOLUTION |
WOS类目 | Multidisciplinary Sciences |
WOS研究方向 | Science & Technology - Other Topics |
URL | 查看原文 |
引用统计 | |
文献类型 | 期刊论文 |
条目标识符 | http://119.78.100.173/C666/handle/2XK7JSWQ/205005 |
专题 | 地球科学 资源环境科学 气候变化 |
作者单位 | 1.Harvard Univ, Dept Earth & Planetary Sci, 20 Oxford St, Cambridge, MA 02138 USA; 2.CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA; 3.Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA 90095 USA |
推荐引用方式 GB/T 7714 | Cao, Hao,Yadav, Rakesh K.,Aurnou, Jonathan M.. Geomagnetic polar minima do not arise from steady meridional circulation[J]. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA,2018,115(44):11186-11191. |
APA | Cao, Hao,Yadav, Rakesh K.,&Aurnou, Jonathan M..(2018).Geomagnetic polar minima do not arise from steady meridional circulation.PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA,115(44),11186-11191. |
MLA | Cao, Hao,et al."Geomagnetic polar minima do not arise from steady meridional circulation".PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 115.44(2018):11186-11191. |
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