Variation of Molecular Ions in the Inner Magnetosphere Observed by the Arase Satellite

Abstract

We analyzed time-of-flight (TOF) data from the Arase satellite to investigate temporal variations of the molecular ion group (O₂⁺, NO⁺, and N₂⁺) at 19.2 keV/q in the inner magnetosphere for 6 years from the solar declining to rising phase. The molecular ions counts were estimated by subtracting the background contamination of oxygen counts. While the number of clear molecular ion events was small, the estimated counts exhibited good correlation with the solar wind dynamic pressure and SYM-H index. Long-term variations of the molecular ions differed from those of counts of the O⁺ and N⁺ group. Additionally, we discuss the importance of the solar wind dynamic pressure in causing variations of molecular ions in the inner magnetosphere.