The Magnetospheric Driving Source of Double-Peak Subauroral Ion Drifts: Double Ring Current Pressure Peaks

Double-peak subauroral ion drifts (DSAIDs), characterized by two high-speed flow channels, is a newly identified flow structure in the subauroral ionosphere. He et al. (2016, https://doi.org/10.1002/2016GL069133) proposed that two region 2 field-aligned currents (R2 FACs) might cause the DSAIDs. However, the underlying physical process that drives the double R2 FACs is unknown. This study reports a DSAIDs event and reveals its magnetospheric drivers. Defense Meteorological Satellite Program F18 satellite observed DSAIDs in the duskside subauroral region, which corresponded well to two low-density troughs and two R2 FACs. The Van Allen Probe B demonstrated that intense substorm ion injections recurrently occurred prior to the formation of DSAIDs, suggesting a potential magnetospheric driver of DSAIDs. Simulation confirms that recurrent ion injections intensify the partial ring current and create double pressure peaks in the near-Earth dusk-to-midnight region, leading two R2 FACs to flow into the ionosphere. The two R2 FACs are thus responsible for the DSAIDs formation. This study unveils the generation mechanism of DSAIDs and deepens the knowledge of the complex magnetosphere-ionosphere system.