Solar cycle, seasonal, and diurnal variations of subauroral ion drifts: Statistical results

The solar cycle, seasonal, and diurnal variations of the subauroral ion drifts (SAIDs) are investigated for the first time to use such a large database of 18,226 SAID events observed by the DMSP satellites during 1987–2012. Statistical results show that SAIDs occur mostly at 60.1° invariant latitude and 2230 magnetic local time with a typical half width of 0.57°, move equatorward during high solar activities with large widths, and have two occurrence peaks in spring and fall equinoxes and two valleys in summer and winter solstices. The seasonal variation of SAID latitude has two valleys in spring and fall, and SAID width has a valley distribution with a minimum in summer. SAIDs exhibit a clear day‐to‐night difference in latitude. The diurnal variation of SAID width has a morning valley and an afternoon peak. The generation mechanism of SAID associated with the electron precipitation and the downward field‐aligned current is also supported in this study.