Systematic Study of Field-aligned Current Sources Based on Satellite Magnetic Field and Particle Precipitation Data

场向电流(FAC)是磁层和电离层之间耦合的基本要素。该项目将使用DMSP-F7和-F11至-F15卫星的磁场和粒子降水数据，对大范围的FAC和粒子降水进行统计检查。识别FAC结构的自动程序将应用于磁场数据集，这将创建一份近300,000个FAC过境点的清单。类似地，已经开发了一种方法，可以利用DMSP数据集来识别粒子降水区域和边界。结合这两种方法将有可能确定FAC的来源区域。白天和晚上的FACS将分别进行检查。对于白天FAC，需要解决的问题是(1)每个FAC系统中不同降水区(区域2、区域1和区域0)的出现频率，以及对MLT和FAC极性的依赖；(2)粒子边界相对于FAC边界的位置；以及(3)结果对太阳风条件的依赖。(1)降水边界相对于第1区和第2区洋流边界的位置；(2)FAC三片结构的位置和边界，这可能与午夜前扇区的Harang不连续有关；(3)结果与地磁条件有关。该项目将使人们更好地了解高纬度粒子降水，这是确定电离层电导率的一个重要因素，因此，它将有助于全球建模和数据同化等空间气象举措。

Field-aligned currents (FAC) are an essential element of the coupling between the magnetosphere and the ionosphere. This project will statistically examine large-scale FACs and particle precipitation using the magnetic field and particle precipitation data from the DMSP-F7 and -F11 to -F15 satellites. An automatic procedure to identify FAC structures will be applied to the magnetic field data set, which will create a list of nearly 300,000 FAC crossings. Similarly, a method has been developed that can identify particle precipitation regions and boundaries, using the DMSP data set. Combining these two methods will make it possible to define the source regions of FACs. Dayside and nightside FACs will be examined separately. For dayside FACs, issues to be addressed are (1) the occurrence frequency of different precipitation regions in each FAC system (region 2, region 1, and region 0), and the dependence on MLT and FAC polarity; (2) the locations of particle boundaries relative to FAC boundaries; and (3) the dependence of the results on solar wind conditions. Issues to be addressed for nightside FACs are (1) the locations of precipitation boundaries relative to the boundaries of region 1 and region 2 currents, (2) the locations and boundaries for 3-sheet structures of FACs, which are presumably related to the Harang discontinuity in the pre-midnight sector; and (3) dependence of the results on geomagnetic conditions. The project will provide a better understanding of high-latitude particle precipitation, which is an important factor to determine the ionospheric conductivity, and therefore, it will contribute to space weather initiatives such as global modeling and data assimilation.