Multi-instrument observations of low-latitude topside plumes after sunrise during the recovery phase of the 27-29 May 2017 magnetic storm

Based on a variety of observation instruments, we have comprehensively analysed the rare topside fossil plumes after sunrise during the recovery phase of the 27-29 May 2017 magnetic storm over Sanya. The results showed that the irregularities leading to these topside plumes on Sanya Very High Frequency (VHF) radar maps were not freshly generated after sunrise, but were able to survive at even ∼02:30UT (∼09:48LT). Different from the fresh equatorial plasma bubbles (EPBs) near sunrise, the |V_d| of these plumes was very small and the zonal drift was also unnoticeable. Although a plasma depletion could be observed by Swarm A satellite near Sanya, it was too small and no ionospheric scintillation or TEC fast fluctuation was caused by it. Since the simultaneous disturbances were found under the F peak over Sanya and the corresponding plumes at Fuke appeared later than those at Sanya by ∼40 min, it was inferred that the irregularities leading to these topside plumes were generated somewhere to the south of Sanya, and then grew and reached higher altitudes and extended to higher latitudes along the geomagnetic field lines. Combining the theory of disturbance electric field during storm, it was inferred that the eastward overshielding penetration electric field as well as the uplift of F layer supported the formation and sustainment of the irregularities leading to the topside plumes.