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

地球磁场正在迅速减弱，导致一些人提出，它将经历崩溃，然后恢复到正常的强度，但方向相反，这种现象被称为“极性反转”，发生在大约80万年前。这样的崩塌将对磁场保护我们免受宇宙射线轰击的能力产生潜在的毁灭性影响，将我们的电网置于严重危险之中，等等。如此剧烈的事件发生的概率取决于磁场的平均强度。如果平均值大致等于现在的磁场(正如许多研究人员假设的那样)，那么磁场迅速下降的事实将比磁场比平均值高得多的情况更令人担忧，因为目前南极洲古代磁场的数据暗示了这一点。关于平均场强的争论源于对其估计的困难。这项提案中倡导的新方法将使研究人员能够获得南纬高纬度的可靠数据集，这将大大增强对估计古代平均磁场强度的信心，有助于我们评估地球磁场灾难性坍塌的可能性。当人们研究古代磁场强度随纬度变化的数据时，很明显很难估计过去500万年的平均磁场强度。地球中心与自旋轴对齐的轴向偶极子(条形磁极)很好地近似了地磁场的方向。但是，这种轴向地磁偶极子的信号，即磁场强度从赤道到两极翻了一番，在过去500万年的场强估计数据库中并不是很明显。对于这种令人不安的失败，有几种可能的解释：1)结合来自不同年龄的数据，可能有不同的平均强度导致场状态的不适当比较，2)在高纬度存在场强的下降，可能反映了“切线柱体”的作用，或3)由于选择标准不佳或实验设计不佳而引入的噪声和/或偏差。后者是一种可能的解释，因为从1960年夏威夷熔岩流发布的数据显示了今天在地球表面观察到的整个强度范围，然而来自这一熔岩流的样本都应该有一个不同的值。这一建议得益于开发了新的实验方法、更好的野外战略和一种新的数据选择方法，这将使我们能够通过一项全面的野外活动，从以前研究过的露头岩浆中收集以最有希望的物质为目标的熔岩流样本，从而准确地估计古代的磁场强度。这些将使用最可靠的实验方案进行分析，并遵循被证明拒绝不准确结果的严格选择标准，从而导致对远古磁场强度的准确和精确估计。

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.