Ionospheric oxygen ions dominant bursty bulk flows: Cluster and Double Star observations

Two extreme oxygen-rich bursty bulk flows ( BBFs) with predominant ionospheric O+ ions have been observed on 8 November 2004 by the Cluster and Double Star spacecraft during a strong magnetic storm time period with Dst = - 373 nT. The oxygen densities in two BBFs are found to be 3 - 5 times larger than the hydrogen densities and the oxygen thermal pressures in the BBFs are 8 times higher than the hydrogen thermal pressure. These BBFs are associated with nested magnetic structures and are observed simultaneously by the CLUSTER and the DSP TC-1 spacecraft. Thus, the flow braking region should be greatly pushed inside the usual pressure balance region ( even inside the inner magnetosphere) since the BBF is dominated by oxygen ions. Results in this paper indicate that oxygen dominated BBFs can be formed during a strong magnetic storm time period. The observations made in this paper suggest that singly charged oxygen ions embedded in the BBFs could be carried into the ring current region by bursty flows during very intense magnetic storms.