Assimilative Mapping of Interhemispheric Polar Ionospheric Electrodynamics

地球主磁场的几何形状与条形磁铁的几何形状不同，它的中心只是与地球自转轴倾斜约11度。地磁场的北极位于北地理极向加拿大方向约1200公里处，但其南极位于南极洲南地理极向太平洋方向约1550公里处。这种不对称是由地球磁场的非偶极性引起的，这导致了太阳风等离子体流与地球磁层相互作用中的各种半球差异。因此，太阳风的能量和动量是不对称地沉积到南北极两极电离层的，导致以往研究报道的两极电离层的不同电动力学参数差异很大。随着新仪器技术的发展，重要的是投资开发新的数据同化和反演方法，以确保从新的观测中更完整地提取地球物理信息。磁层-电离层耦合在高纬度电离层对流、场向电流、电磁能量（坡印亭）通量、极光粒子降水和高层大气（热层）响应方面是不对称的。本研究将通过地磁场定向电流和电离层对流电场来量化电磁能量沉积的瞬时半球间不平衡程度，将所有这些变量的量化整合到一个统一的框架中。多种类型的天基和地面观测可以同时进行分析，通过社区电离层电动力学同化测绘（AMIE）软件技术创建一个连贯的全球电离层电动力学半球间图像。过去，与北极地区相比，南极地区缺乏观测资料，因此无法对半球间电离层电动力学变量进行全面分析，除非完全依靠天基观测。最近从南极地区地面磁力计和高频雷达获得的数据正在改变这种情况。提出的研究是及时的，使用了一种创造性的，甚至是变革性的方法，利用了新的全球半球间观测，这些观测可以通过nsf资助的主动磁层和极地电动力学响应实验（AMPERE）、超级双极光雷达网络（SuperDARN）和SuperMAG数据库获得。这将有助于解决迄今为止尚未得到结论性解释的地球空间研究的基本问题。通过对观测资料的广泛同化，将在两极地区对几个电动力变量进行自一致的全球分析。这项研究将对NOAA空间天气预报中心（SWPC）的研究和开发活动做出重大贡献，在该中心，新一代半球间高纬度电动力学AMIE地图可能成为SWPC向美国政府机构提供的服务的一部分，以解决空间天气对全国地面和天基技术系统的负面影响。更新后的AMIE还将成为国家和国际空间科学家之间积极合作的共同平台，这些科学家研究太阳风能量和动量在地球磁层、电离层和热层的全球转移。最后，这项有趣而重要的科学研究通过直接参与研究，为研究生提供了一个理想的教育体验和训练机会。

The Earth's main magnetic field geometry is not similar to that of a bar magnet centered and simply tilted about 11 degrees from the Earth's spin axis. The geomagnetic field has its North Pole located at ~1,200-km of the North Geographic Pole towards Canada, but its South Pole is located about 1,550-km from the South Geographic Pole in Antarctica towards Pacific Ocean. This asymmetry is caused by the non-dipolar nature of the Earth's magnetic field that leads to various hemispherical differences in the interaction of the solar wind plasma flow with the Earth's magnetosphere. Thus the solar wind's energy and momentum are deposited into the polar ionospheres of both the Northern and Southern Polar Regions asymmetrically, causing considerable diversity in different electrodynamic parameters of the polar ionosphere reported in past studies. As new instrumentation techniques are developed, it is important to invest in development of new data assimilation and inverse methods to assure a more complete extraction of geophysical information out of new observations.The magnetosphere-ionosphere coupling is not symmetrical in terms of high-latitude ionospheric convection, field-aligned currents, electromagnetic energy (Poynting) flux, auroral particle precipitation, and upper atmosphere (thermosphere) responses. This study will quantify the degree of instantaneous interhemispheric imbalance of the electromagnetic energy deposition via geomagnetic field-aligned currents and ionospheric convection electric fields, integrating quantification of all these variables into a unified framework. Multiple types of space-based and ground-based observations can be simultaneously analyzed, creating a coherent interhemispheric picture of global ionospheric electrodynamics via the community Assimilative Mapping of Ionospheric Electrodynamics (AMIE) software technique. In the past, the lack of observations in the Southern polar region in comparison with the Northern polar region precluded a comprehensive analysis of interhemispheric ionosphere electrodynamic variables, unless exclusively relying on space-based observations. The recent availability of data from ground-based magnetometers and high frequency (HF) radars in the Southern polar region is changing this situation. The proposed research is timely, using a creative, even transformative approach that takes advantage of new global interhemispheric observations available through the NSF-funded Active Magnetosphere and Polar Electrodynamics Response Experiment (AMPERE), Super Dual Auroral Radar Network (SuperDARN), and SuperMAG database. This will help addressing fundamental questions of geospace research that have eluded conclusive explanation so far. Several electrodynamic variables will be self-consistently analyzed globally in both polar regions via the extensive assimilation of observational data. This study will contribute significantly to the research and development activities at the NOAA Space Weather Prediction Center (SWPC) where a new generation of AMIE mapping of interhemispheric high-latitude electrodynamics may become part of the services provided by SWPC to the U.S. Government agencies that address negative effects of space weather on the nationwide ground- and space-based technological systems. The updated AMIE will also become a common platform for active collaboration among national and international space scientists who study the global transfer of solar wind energy and momentum into the Earth's magnetosphere, ionosphere, and thermosphere. At last, this interesting and important scientific research provides an ideal opportunity for educational experience and training for a graduate student through direct involvement in the study.