Accomplishment Based Renewal: Transforming the paleointensity experiment and application to the paleointensity database

基于成就的更新：将古强度实验和应用转变为古强度数据库

• 批准号: 1547263
• 负责人: Lisa Tauxe
• 金额: $ 39.55万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-02-15 至 2021-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1547263&HistoricalAwards=false
• 关键词: Accomplishment; Based; Renewal; Transforming; paleointensity

The geomagnetic field has been dropping rapidly over the past century (8%)leaving some worried that it could collapse into what is known as a 'transitional state' with a strength of ~10% of the present field. Such an event would pose severe danger to the planet's electrical grid and satellites requiring some advanced planning. The likelihood of this happening is presently unknown as human measurements of the magnetic field strength span only the last ~150 years and fundamental questions regarding the average field strength of the geomagnetic field and its variation through time remain despite decades of effort. This project will serve to support the research of several students (both undergraduate and graduate), one of whom is an under-represented minority female. In addition, it will provide funding for a female computer programmer to continue efforts on improving the software supporting online materials including a textbook and a complete software package (PmagPy) that integrates smoothly with the MagIC database, (http://earthref.org/MAGIC/books/Tauxe/Essentials and http://earthref.org/PmagPy/cookbook respectively).The signal of an axial geomagnetic dipole, whereby the field strength doubles from the equator to the poles, is readily apparent in the present field but no such clear dipolar signal exists in the paleointensity database 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 flow on Hawaii display the entire range of intensity values observed on the Earth's surface today, yet they should all have one distinct value. The PI has developed new experimental methods, better field strategies and a new approach to data selection that will allow the team to obtain accurate estimates of the ancient field strength to improve our understanding of the intensity behavior in Earth's past. The PI plans a comprehensive field campaign to collect samples targeting the most promising material for paleointensity study. 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 paleointensity estimates. The PI will also complete a long term aging experiment of thermal remanence to investigate the contribution of bias (andnoise) of non-single domain material in the database, with an eye toward improving the experiment and data selection procedures leading to higher accuracy in paleointensity estimates.

在过去的世纪，地磁场一直在迅速下降（8%），这让一些人担心它可能会崩溃到一个所谓的“过渡状态”，强度只有现在的10%。 这样的事件将对地球的电网和卫星构成严重威胁，需要一些先进的计划。 这种情况发生的可能性目前尚不清楚，因为人类对磁场强度的测量仅持续了近150年，尽管经过数十年的努力，但关于地磁场平均场强及其随时间变化的基本问题仍然存在。 该项目将有助于支持几名学生（本科生和研究生）的研究，其中一人是代表性不足的少数民族女性。 此外，它还将资助一名女计算机程序员继续努力改进支持在线材料的软件，包括一本教科书和一个与MagIC数据库顺利整合的完整软件包（PmagPy）（分别为http：earthref.org/MAGIC/books/Tauxe/Essentials和http://earthref.org/PmagPy/cookbook）。在目前的领域中是显而易见的，但在过去五百万年的古强度数据库中不存在这样清晰的偶极信号。对于这种令人不安的失败有几种可能的解释：1）将不同年龄的数据与可能不同的平均强度相结合，导致场状态的不适当比较，2）在高纬度处存在场强的降低，可能反映了“切向圆柱体”的作用，或者3）存在由不良选择标准或不良实验设计引入的噪声和/或偏差。后者是一个可能的解释，因为1960年夏威夷的流动数据显示了今天在地球表面观察到的整个强度值范围，但它们都应该有一个不同的值。PI开发了新的实验方法，更好的场策略和新的数据选择方法，使团队能够获得对古代场强的准确估计，以提高我们对地球过去强度行为的理解。PI计划开展一项全面的实地活动，收集针对最有希望用于古强度研究的材料的样本。这些将使用最强大的实验协议进行分析，并受到严格的选择标准证明拒绝不准确的结果，从而导致准确和精确的古强度估计。PI还将完成热剩磁的长期老化实验，以调查数据库中非单畴材料的偏差（和噪声）的贡献，着眼于改进实验和数据选择程序，从而提高古强度估计的准确性。

项目成果

Investigating the Accuracy, Precision, and Cooling Rate Dependence of Laboratory‐Acquired Thermal Remanences During Paleointensity Experiments

• DOI: 10.1029/2018gc007946
• 发表时间: 2019-01
• 期刊: Geochemistry
• 影响因子: 3.7
• 作者: C. N. Santos;L. Tauxe

Domain State Diagnosis in Rock Magnetism: Evaluation of Potential Alternatives to the Day Diagram

• DOI: 10.1029/2018jb017049
• 发表时间: 2019-06
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: A. Roberts;P. Hu;R. Harrison;D. Heslop;A. Muxworthy;H. Oda;Tetsuro Sato;L. Tauxe;Xiang Zhao

Thermomagnetic recording fidelity of nanometer-sized iron and implications for planetary magnetism

• DOI: 10.1073/pnas.1810797116
• 发表时间: 2019-02-05
• 期刊: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• 影响因子: 11.1
• 作者: Nagy, Lesleis;Williams, Wyn;Ferreira, Idenildo
• 通讯作者: Ferreira, Idenildo

From Nano to Micro: Evolution of Magnetic Domain Structures in Multidomain Magnetite

• DOI: 10.1029/2019gc008319
• 发表时间: 2019-06-01
• 期刊: GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
• 影响因子: 3.5
• 作者: Nagy, Lesleis;Williams, Wyn;Muxworthy, Adrian R.
• 通讯作者: Muxworthy, Adrian R.

A Critical Appraisal of the “Day” Diagram

• DOI: 10.1002/2017jb015247
• 发表时间: 2017-12
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: A. Roberts;L. Tauxe;D. Heslop;Xiang Zhao;Zhaoxia Jiang