Solar Wind Control of Alfven Wave Power in the Polar Region

该项目将量化阿尔芬波在极地地区的全球分布及其随太阳风条件、地磁暴条件和极光亚暴阶段的变化。 阿尔芬波是地球磁层内动力学和相关能量传输的重要组成部分。 随着每一颗卫星进入磁层的使命，这一点变得越来越明显。 卫星在穿过等离子体片、等离子体层、尾叶、极光带和磁尾重连区时，都观测到了显著的阿尔芬波活动。阿尔芬波是沿沿着磁场线传播的振荡。就像把石头扔进水里，波会向外移动一样，阿尔芬波会把磁场或电流变化的信息沿着磁场线沿着传播到其他地方。 在这些其他位置，波可以被耗散，提供它们的能量来为远离原始能源的不同过程提供动力。例如，在极地电离层中，阿尔芬波的消散提供了能量，加速了负责创造令人惊叹的极光的电子。这些阿尔芬波被认为起源于远离极地电离层的伸展磁尾内的强等离子体射流。 该项目将在夏季资助一名研究生，从而为下一代科学工作者的培训做出贡献。在对磁层动力学具有重要意义的能量传输过程的知识方面取得的进展，从长远来看，将改进空间气象预报模型，对技术社会具有价值，这里提出的项目将绘制美国航天局极地航天器观测到的阿尔芬波功率统计图，并量化这些图如何根据太阳风和行星际磁场参数以及风暴和亚风暴条件而变化。将MHD建模的结果与统计图进行比较，以验证MHD模拟。本研究将使用与PI早期工作相似的工具和方法，但将包括10年的数据，而不是之前使用的1年间隔。这将使统计检查阿尔芬波功率的各种不同的条件和地磁活动水平。对地球空间系统的能量输运和动力学的新见解。

This project will quantify the global distribution of Alfven waves in the polar region and its variations with solar wind conditions, geomagnetic storm conditions, and auroral substorm phase. Alfven waves are an essential component of the dynamics and associated energy transport within the Earth's magnetosphere. This has become more and more apparent with each satellite mission into the magnetosphere. Significant Alfven wave activity has been observed by satellites traveling through the plasma sheet, the plasmasphere, the tail lobes, the auroral zone, and the reconnection regions in the magnetotail. Alfven waves are oscillations traveling along magnetic field lines. Much like waves moving outward from a stone tossed into the water, the Alfven waves carry information to other locations along magnetic field lines about changes in the magnetic field or currents at the site of their generation. At these other locations, the waves can be dissipated supplying their energy to power different processes remote from the original energy source. For example, in the polar ionosphere, the dissipation of Alfven waves supplies energy to accelerate the electrons responsible for creating breathtaking auroras. These Alfven waves are thought to originate in strong plasma jets within the stretched magnetotail far from the polar ionosphere. The project will support a graduate student for the summer thus contributing to the training of the next generation scientific workforce. The advances in knowledge of an energy transport process important to the dynamics of the magnetosphere will in the long term improve models of space weather forecasting, of value to a technological society.The project proposed here will develop statistical maps of Alfven wave power observed by the NASA Polar spacecraft and quantify how these maps vary depending on solar wind and interplanetary magnetic field parameters and storm and substorm conditions. Results from MHD modeling will be compared to the statistical maps to validate the MHD simulations. The study will use tools similar to and the methodology of earlier work by the PI, but will include 10 years of data instead of the one-year interval used previously. This will allow the statistical examination of Alfven wave power for a wide-range of different conditions and geomagnetic activity levels. New insights about energy transport and dynamics of the Geospace system are expected.