Statistical characteristics of the equatorial boundary of the nightside auroral particle precipitation

Based on the auroral electron/ion precipitation boundary database observed by the DMSP satellites during 1984–2009, the characteristics of the nightside equatorial boundaries of the electron precipitation (B1E) and the ion precipitation (B1I) in the Northern/Southern Hemispheres (NH/SH) are statistically investigated. The results show: That most of the boundaries are located between magnetic latitude (MLAT) of 60°–70° with the mean MLAT for B1E/B1I to be 64.30°N/63.22°N and 64.48°S/63.26°S in the NH and SH, respectively, indicating that B1E and B1I in both hemispheres are located in conjugated magnetic field lines with B1E ∼1.2° poleward of B1I; that the MLAT of B1E and B1I in both hemispheres shift to lower MLAT (from ∼70° to ∼55°) as geomagnetic activity increases; that MLAT of both B1E and B1I and their differences slowly decrease from dusk to midnight with some difference in both hemispheres during different levels of geomagnetic activities; that B1E and B1I in both hemisphere decrease linearly with Kp and exponentially with Dst, AE, and SYM-H, respectively, demonstrating that auroral particle precipitation is closely related with geomagnetic activity; that in different magnetic local time (MLT) sectors, the changing rates of the boundaries with Kp are different, and the rates of B1E are generally larger than that of B1I, implying that the difference between B1E and B1I reduce with increasing geomagnetic activity. Compared with previous studies, the statistical results based on the long-term large database in this paper can well reflect the properties of the equatorial boundaries of auroral precipitation and may be used for physical modeling or space weather forecasting in future.