Variations of N⁺/O⁺ in the ring current during magnetic storms

Based on the energetic particle measurements obtained by CRRES/MICS, variations of the third most important ion species, N⁺, in the ring current region have been investigated in detail. The ratio of N⁺/O⁺ during geomagnetic quiet times is found to be about 0.314 ± 0.043 and decreases with enhanced solar radiation, as indicated by the F10.7 index. Through a statistic study, the ratio of N⁺/O⁺ has been demonstrated to decrease with enhanced geomagnetic activity for strong storms, whereas for small storms, there is no obvious correlation found for this ratio. It is worthy to note that not all the values during active times are higher than those at quiet times. The quite different ratios of N⁺/O⁺ (up to 50%) in the ring current region found between quiet and storm times in this paper, together with the different combination rates of atomic oxygen and nitrogen, suggest that the ionospheric nitrogen ions may play a crucial role during some magnetic storms and should have a strong impact on the magnetic storm simulation works on the build-up and/or decay processes of the ring current.