| 项目编号: | 1541285
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| 项目名称: | Finding the Missing Geomagnetic Dipole Signal in Global Pleointensity Data: Revisiting the High Southerly Latitudes |
| 作者: | Lisa Tauxe
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| 承担单位: | University of California-San Diego Scripps Inst of Oceanography
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| 批准年: | 2016
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| 开始日期: | 2016-06-01
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| 结束日期: | 2019-05-31
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| 资助金额: | 416287
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| 资助来源: | US-NSF
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| 项目类别: | Standard Grant
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| 国家: | US
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| 语种: | 英语
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| 特色学科分类: | Geosciences - Polar
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| 英文关键词: | field strength
; magnetic field
; ancient field strength
; datum
; year
; lava flow
; axial dipole
; geomagnetic field
; high southerly latitudes
; axial geomagnetic dipole
; robust data set
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| 英文摘要: | The geomagnetic field is decreasing rapidly, leading some to propose that it will undergo collapse followed by a return to its usual strength but in the opposite direction, a phenomenon known as a "polarity reversal" which happened last approximately 800,000 years ago. Such a collapse would have a potentially devastating effect on the ability of the magnetic field to shield us from cosmic ray bombardment, placing our electrical grid at grave risk, among other things. The probability of such a drastic event happening depends on the average strength of the magnetic field. If the average is approximately equal to the present field (as many researchers assume), then the fact that the field is dropping rapidly would be more alarming than if the magnetic field is quite a bit higher than average, as implied by the current data for the ancient magnetic field from Antarctica. The argument over the average field strength stems from the difficulty of its estimation. The new approach advocated for in this proposal will allow researchers to obtain a robust data set for high southerly latitudes which will greatly enhance confidence in estimates of the average ancient field strength, contributing to our ability to assess the likelihood of catastrophic collapse of the geomagnetic field.
The difficulty in estimating the average magnetic field strength over the past five million years is apparent when one examines data for ancient field strength as a function of latitude. Directions of the geomagnetic field have been well approximated by an axial dipole (bar magnetic) at the center of the Earth that is aligned with the spin axis. But the signal of such an axial geomagnetic dipole, whereby the field strength doubles from the equator to the poles, is not readily apparent in the database of field strength estimates from the last five million years. There are several possible explanations for this troubling failure: 1) combining data from different ages with possibly different average intensities leads to an inappropriate comparison of field states, 2) there is a depression of field strength at high latitude, perhaps reflecting the role of the `tangent cylinder?, or 3) there is noise and/or bias introduced by poor selection criteria or poor experimental design. The latter is a likely explanation as published data from the 1960 lava flow on Hawaii display the entire range of intensity values observed on the Earth's surface today, yet samples from this lava flow should all have one distinct value. This proposal benefits from the development of new experimental methods, better field strategies and a new approach to data selection that will allow accurate estimation of the ancient field strength through a comprehensive field campaign to collect lava flow samples from previously studied outcrops targeting the most promising material. These will be analyzed using the most robust experimental protocol and subjected to rigorous selection criteria proven to reject inaccurate results, leading to both accurate and precise estimates of ancient field strength. |
| 资源类型: | 项目
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/92264
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| Appears in Collections: | 全球变化的国际研究计划
科学计划与规划
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| Recommended Citation: | |
Lisa Tauxe. Finding the Missing Geomagnetic Dipole Signal in Global Pleointensity Data: Revisiting the High Southerly Latitudes. 2016-01-01.
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