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

在过去的一个世纪里，地磁场一直在迅速下降（下降了8%），这让一些人担心它可能会崩溃，进入所谓的“过渡状态”，强度约为目前磁场的10%。这样的事件将对地球的电网和卫星构成严重威胁，需要一些先进的规划。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，尽管经过了几十年的努力，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。该项目将用于支持几名学生（本科生和研究生）的研究，其中一名学生是代表性不足的少数民族女性。此外，它还将为一名女性计算机程序员提供资金，继续努力改进支持联机材料的软件，包括一本教科书和一个与MagIC数据库顺利结合的完整软件包（PmagPy）（分别为http://earthref.org/MAGIC/books/Tauxe/Essentials和http://earthref.org/PmagPy/cookbook）。轴向地磁偶极子的信号，即磁场强度从赤道到两极加倍的信号，在目前的磁场中很明显，但在过去500万年的古强度数据库中却没有这种明显的偶极子信号。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，导致对场态的不适当比较，2)高纬度地区场强下降，可能反映了“切线圆柱体”的作用，或者3)存在噪声和/或由不良选择标准或不良实验设计引入的偏差。后者是一种可能的解释，因为1960年夏威夷流的公布数据显示了今天在地球表面观测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，更好的野外策略和一种新的数据选择方法，这将使团队能够准确估计古代磁场强度，从而提高我们对地球过去强度行为的理解。PI计划进行一次全面的野外活动，以收集最有希望用于古强度研究的材料为目标。这些将使用最可靠的实验方案进行分析，并服从严格的选择标准，以证明拒绝不准确的结果，从而获得准确和精确的古强度估计。PI还将完成热残余的长期老化实验，以研究数据库中非单畴材料的偏差（和噪声）的贡献，并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。

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.