Collaborative Research: GEM: Investigation of UT Dependence of Magnetic Storm Strength

这是一个为期三年的项目，旨在研究一个引人注目的新发现，即地磁风暴的强度表现出明显的普遍时间依赖性，并且在风暴期间随着中纬度电离层等离子体丰度的变化而变化。地磁指数为我们提供了自上个世纪地球空间产生以来发生的物理过程的最一致的度量。最值得注意的是，地磁风暴的强度是通过所谓的Dst指数来捕捉的，Dst指数是由一组位于全球各地的四个地面磁力计测量结果计算出来的。该项目将利用新导出的改进的夏时制指数数据集，详细检查风暴时间夏时制与UT、季节和太阳周期的趋势。电离层等离子体极大地增加了磁层中的压力、压力梯度和电流，后者是在地面上测量来指示磁暴强度的。极光带的离子外流，特别是在日光侧？尖端？而夜侧尾巴重联区，提供了大部分的等离子体。高纬度地区电离层等离子体的丰度最近被证明是一个比以前认为的更复杂的过程，在磁场活动增强期间，有许多过程以快速的方式将等离子体从中纬度地区输送到高纬度地区。磁暴强度的变化可能是在磁暴活动增强期间由ut决定的外流调制造成的。研究电离层离子流入磁层在不同风暴期间如何变化，并影响Dst指数的UT依赖性，是本项目的主要总体目标。另一项平行研究将检验观测中的UT依赖是否也可由耦合物理系统的第一性原理模型再现。该项目将使用电离层-热层-磁层模型套件，这些模型构成了密歇根大学空间天气模型框架。该项目的影响超出了提高科学认识的直接好处。密歇根大学和伯克利分校的学生将参与这项工作的各个方面，结果将提交给广泛阅读的出版物，该团队将与伯克利科学教育中心合作，使研究结果能够与全国各地的磁力计数据和磁学教师网络合作。确定美国夏季下午的磁暴是否确实更强的重要性怎么强调都不为过，特别是考虑到美国国家科学院最近关于一场真正的大型地磁风暴对美国可能造成的经济损失的研究结果。

This is a three-year project to investigate a remarkable new finding, that the intensity of geomagnetic storms displays distinct universal time dependence, and that it varies in concert with middle latitude ionospheric plasma abundance during storms. Geomagnetic indices provide our most consistent measure of physical processes occurring in geospace since their creation over the last century. The strength of geomagnetic storms, most notably, is captured in the so-called Dst index, calculated from a set of four ground-based magnetometer measurements located strategically around the Globe. This project will utilize a newly derived, improved Dst index dataset to carry out a detailed examination of trends in the storm-time Dst with UT, season and solar cycle. Ionospheric plasma adds greatly to the pressure, pressure gradients, and currents in the magnetosphere, the last of which are measured on the ground to indicate magnetic storm strength. Ion outflow in the auroral zone, particularly in the dayside ?cusp? and nightside tail-reconnection region, provides most of this plasma. The abundance of ionospheric plasma at high latitudes has recently been shown to be a more complex process than previously thought, with a number of processes delivering plasma from middle to high latitudes in rapid fashion during periods of enhanced magnetic activity. A UT-dependent modulation of outflow during enhanced magnetic activity is one possible explanation for the observed variation in magnetic storm strength. The examination of how ionospheric ion outflow into the magnetosphere may vary during different storms and impact the UT dependence of the Dst index is the main overarching objective for this project. A parallel effort will examine whether the UT dependence in the observations is also reproduced by first-principles models of the coupled physical system. The project will use the suite of ionosphere-thermosphere-magnetosphere models that make up the University of Michigan Space Weather Modeling Framework.The project has impacts beyond the immediate benefits of improved scientific understanding. Students will participate in all aspects of the work, both at U. Michigan and Berkeley, results will be submitted to widely-read publications, and the team will work with the Center for Science Education at Berkeley to make the findings accessible to the network of teachers that it works with around the country on magnetometer data and magnetism. The importance of determining whether magnetic storms are indeed more powerful in the afternoon in the United States during summer can hardly be overstated, particularly in light of recent National Academy findings of the likely economic costs to the U.S.A. of a truly major geomagnetic storm.