Mixture of two oxygen ion populations in the magnetosheath under northward IMF

During the recovery phase of November 6, 2001 superstorm, Cluster observed two distinct single charged oxygen ion populations in the duskside magnetosheath. One of them featured tailward and continuous flow with energy band (0.4-4 keV); the other one also showed tailward flow, but it looked busty-like with higher energy (> 10 keV). These oxygen ions escaped from the magnetosphere via different paths and finally mixed in the magnetosheath. We have investigated the busty oxygen ion flows. Our results suggest that they might not originate from the storm ring current but directly came from the polar ionosphere, and then accelerated by the intermittent magnetic reconnection in the high-latitude magnetopause. The magnetic reconnection created a series of magnetic flux ropes, by which the busy-like energy oxygen ions mixed with the low oxygen flow. Though there was no in-situ observations at the high-latitude magnetopause, the particle precipitations measured by DMSP on the ionosphere altitude verified the existence of magnetic reconnection.