A comparison of small-scale magnetic fluctuations in the Region 1 and 2 field-aligned current systems

Abstract

By determining the location and size of the Region 1 (R1) and Region 2 (R2) large‐scale field‐aligned currents (FACs) from Active Magnetosphere and Planetary Electrodynamics Response Experiment data, we are able to study the small‐scale magnetic fluctuations observed by the Swarm satellites embedded within the large‐scale FACs. A statistical comparison of R1 and R2 high‐frequency fluctuations is presented in terms of different solar wind conditions and geomagnetic activities. We find that (1) the amplitude of high‐frequency fluctuations in both R1 and R2 increases as the large‐scale R1 and R2 FACs intensify; (2) high‐frequency fluctuations in R1 peak near dayside dawn and dusk, while those in R2 peak around noon; (3) the location of the largest high‐frequency fluctuations in R1 shifts in local time in response to IMF By, indicating a connection between the R1 fluctuation and the driving solar wind most likely explained by magnetic reconnection; and (4) high‐frequency fluctuations in R2 are enhanced in a small region near local noon and respond clearly to nightside drivers, as characterized by the auroral electrojet index. Our analysis shows that the intensity of R1 and R2 high‐frequency magnetic fluctuations is directly connected to the intensity of FACs, which implies that the magnetic fluctuations are closely related to the magnetospheric processes that drive them. © 2017 American Geophysical Union