Finding the Missing Geomagnetic Dipole Signal in Global Pleointensity Data: Revisiting the High Southerly Latitudes

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项目编号	1541285
	Finding the Missing Geomagnetic Dipole Signal in Global Pleointensity Data: Revisiting the High Southerly Latitudes
	Lisa Tauxe
主持机构	University of California-San Diego Scripps Inst of Oceanography
项目开始年	2016
	2016-06-01
项目结束日期	2019-05-31
资助机构	US-NSF
项目类别	Standard Grant
项目经费	416287(USD)
国家	美国
语种	英语
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.
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文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/69624
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Lisa Tauxe.Finding the Missing Geomagnetic Dipole Signal in Global Pleointensity Data: Revisiting the High Southerly Latitudes.2016.