Small-Scale Field-Aligned Currents of Intense Amplitude Resolved by the Swarm Satellites

In this study we used the Level-2 product of field-aligned currents (FACs) from the Swarm satellites, to check the distribution characteristics of small-scale FACs (SSFACs) of intense amplitude. Data applied covers 9 years from December 2013 to April 2023. Based on the statistical analysis on the amplitude, the SSFACs in this study is defined with amplitude larger than 20 mu A/m2, which is also by two orders larger than the well-known large-scale R1 and R2 FACs (about 0.2 mu A/m2). Such an intense amplitude indicates that it should play an important role in the magnetosphere-ionosphere coupling. The location of the SSFACs observed is general between 60 degrees similar to 80 degrees and -80 degrees similar to-60 degrees magnetic latitude, which is coincidently inside the auroral oval. The occurrence of the SSFACs depends on both solar activity and geomagnetic activity, and the influence of geomagnetic activity is more important than that of solar activity. By further checking the simultaneous in situ plasma density measured by Swarm, we find that the SSFACs are always associated with clear plasma density fluctuations. This suggests that the SSFACs play an important role for causing the small-scale plasma density irregularities at auroral latitude. The small-scale field-aligned currents (SSFACs) play an important role for causing the small-scale plasma density irregularities at auroral latitude SSFACs depends on solar and geomagnetic activity, and the influence of geomagnetic activity is more important than that of solar activity SSFACs are mainly observed coincidently inside the auroral oval