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

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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.