Assimilative Mapping of Interhemispheric Polar Ionospheric Electrodynamics

地球的主磁场几何形状与条形磁铁的几何形状不同，磁铁的中心位置与地球自转轴倾斜约11度。地磁场的北极位于北极向加拿大约1200公里处，而南极位于南极洲南极向太平洋方向约1 550公里处。这种不对称性是由地球磁场的非偶极性质造成的，这导致了太阳风等离子体流与地球磁层相互作用的不同半球差异。因此，太阳风的能量和动量不对称地沉积到南北极地的极地电离层中，导致以往研究报告的极地电离层的不同电动力学参数存在相当大的差异。随着新仪器技术的发展，必须投资开发新的数据同化和反演方法，以确保从新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。这项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。可以同时分析多种类型的天基和陆基观测数据，通过电离层电动力学社区同化测绘(AMIE)软件技术创建全球电离层电动力学的相干半球间图像。过去，由于南极区与北极区相比缺乏观测，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。最近从南极地区的地面磁力计和高频雷达获得的数据正在改变这一状况。拟议的研究是及时的，采用了一种创造性的、甚至是变革性的方法，该方法利用了美国国家科学基金会资助的活动磁层和极地电动力学响应实验、超级双极光雷达网和SuperMAG数据库提供的新的全球半球间观测。这将有助于解决地球空间研究的基本问题，这些问题到目前为止还没有得到确凿的解释。几个电动力学变量将通过广泛的观测数据同化在两个极地区域进行全球自洽分析。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，在那里，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，这些服务旨在解决空间天气对全国地面和天基技术系统的负面影响。更新的AMIE还将成为国内和国际空间科学家积极合作的共同平台，他们研究太阳风能和动量向地球磁层、电离层和热层的全球转移。最后，这一有趣而重要的科学研究为研究生提供了一个通过直接参与学习来获得教育经验和培训的理想机会。

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.