The effects of long-term changes in the Earth's magnetic field on the atmosphere: understanding the past; predicting the future

“地球磁场长期变化对大气层的影响：了解过去;预测未来“该项目研究地球内部磁场变化对大气层和气候的影响。地球的磁场在最近一段时间内变化相对较快。在过去的十年中，北磁极的位置一直在以迄今为止最快的速度移动，达到40-60公里/年。此外，自1840年以来，磁场强度一直以每世纪5-7%的速度稳步下降，这导致了我们可能正在走向磁场逆转的猜测。一些研究发现，地球磁场的变化与气候参数之间存在相关性。然而，这一联系的负责机制仍然难以捉摸。该项目将研究地球磁场影响气候的一个可能途径，即从高层大气（~100-500公里）开始的变化向下传播。这是一个以前从未被研究过的新想法。地球磁场的变化直接影响电离层（高层大气的带电部分）和磁层（地球周围保护我们免受太阳风影响的气泡）。我们将使用耦合磁层-电离层-热层（CMIT）模型进行模拟，研究和量化自1600年以来发生的地球磁场历史变化对耦合高层大气和磁层系统的影响。所发现的反应将与观测到的高层大气长期趋势和地磁活动指数进行比较，后者衡量电离层和磁层电流系统对地球主磁场的扰动。我们还将探索一些潜在的未来情景，通过外推当前的磁场变化到未来50-200年，然后我们研究在高层大气中发现的影响在多大程度上影响了中层和低层大气。我们将使用全大气群落气候模式（WACCM）来完成这项工作，这是一个从地表延伸到高层大气的数值模式，与CMIT模式部分重叠。在其顶部，WACCM将被迫与项目第一部分中发现的高层大气响应。我们将确定这些强迫的向下传播是否会引起下面大气的显著变化。对流层的任何重大反应都将与磁场变化和已观测到的气候参数之间的相互关系进行比较，通过研究过去四个世纪以来磁场变化对气候的影响，该项目有助于更好地量化大气变化的自然来源。这对于正确地确定观测到的气候趋势和更精确地评估人为对气候的影响是必要的。这两者对于制定减缓战略和准确预测未来气候都至关重要。该项目还提供了对磁场变化的影响的第一次洞察，我们可以预期在未来。特别是磁场逆转几乎肯定会对高层大气和地球空间环境以及该环境所承载的技术系统产生巨大影响。然而，对气候的影响很难预测，因为我们目前不知道地球磁场会以何种方式以及在多大程度上影响气候。拟议的项目将是增进我们对地球磁场与气候之间联系的了解的第一步。

"The effects of long-term changes in the Earth's magnetic field on the atmosphere: understanding the past; predicting the future"This project investigates the effects of changes in the Earth's internal magnetic field on the atmosphere and climate. The Earth's magnetic field has been changing relatively rapidly in recent times. During the last decade, the position of the north magnetic pole has been moving at its fastest rate recorded so far, at 40-60 km/year. In addition, the magnetic field strength has been steadily decreasing at a rate of 5-7% per century since 1840, which has led to speculations that we may be heading for a magnetic field reversal. Some studies have found correlations between changes in the Earth's magnetic field and climate parameters. However, the responsible mechanism for this link has remained elusive. This project will investigate one possible pathway by which the Earth's magnetic field could affect climate, namely the downward propagation of changes initiated in the upper atmosphere (~100-500 km). This is a novel idea that has not been investigated before.Changes in the Earth's magnetic field directly influence the ionosphere, the charged portion of the upper atmosphere, and the magnetosphere, the bubble around the Earth that shields us from the solar wind. We will examine and quantify the effects of historical changes in the Earth's magnetic field that have occurred since 1600 on the coupled upper atmosphere and magnetosphere system, using simulations with the Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) model. The responses found will be compared to observed long-term trends in the upper atmosphere and indices of geomagnetic activity, which measure perturbations to the Earth's main magnetic field as a result of ionospheric and magnetospheric current systems. We will also explore some potential future scenarios by extrapolating current magnetic field changes into the next 50-200 years.We then investigate to what extent the effects found in the upper atmosphere influence the middle and lower atmosphere. We will do this using the Whole Atmosphere Community Climate Model (WACCM), a numerical model that extends from the surface to the upper atmosphere, partly overlapping with the CMIT model. At its top, WACCM will be forced with the upper atmospheric responses found in the first part of the project. We will determine whether downward propagation of these forcings causes a significant change in the atmosphere below. Any significant response in the troposphere will be compared to the correlations between magnetic field changes and climate parameters that have been observed.By studying the effects of magnetic field changes on the climate over the past four centuries, this project contributes to a better quantification of natural sources of atmospheric variability. This is needed to attribute observed climate trends correctly and assess man-made effects on climate more precisely. Both are essential for developing mitigation strategies and for making accurate predictions of future climate. The project also offers a first insight into the effects of magnetic field changes that we can expect in the future. Especially a magnetic field reversal would almost certainly have dramatic consequences for the upper atmosphere and geospace environment, and the technological systems this environment hosts. However, the effects on climate are very hard to predict, as we currently do not know in what ways and to what extent the Earth's magnetic field can affect climate. The proposed project will be a first step in improving our understanding of the link between the Earth's magnetic field and climate.