Observational evidence of ionospheric feedback effect in generating throat aurora

Ionospheric feedback effect has been proposed as a key factor in the formation of the throat aurora. Theoretically, it acts through the ionospheric feedback instability (IFI) induced by localized ionospheric density enhancements. However, observations linking ionospheric density enhancements to throat auroras remain lacking. In this study, we selected 70 throat auroras from DMSP/SSUSI images spanning from 2005 to 2010, combined with reliable GPS total electron content (TEC) data. Statistical analysis of these events reveals that 50 throat auroras (~71.4%) were preceded by plume-like TEC enhancements. These enhanced TEC structures generally extended from low latitudes into the high-latitude noon sector (10–14 MLT, ≥70° MLAT), persisting for an average of ~30.8 minutes within this region and being parallel to subsequent throat auroras. Further, case studies of two typical events show that the electron precipitations of throat auroras occurred adjacent to the duskward boundaries of these enhanced TEC plumes. This spatial correlation between ionospheric density enhancements and auroral structures is consistent with the features of the IFI theory. Also, the density gradients along the boundaries favor the establishment of IFI. Therefore, these observations establish a clear link between ionospheric density enhancements and throat auroras, providing critical evidence for the ionospheric feedback mechanism in generating the throat aurora. Our findings also highlight the importance of ionospheric feedback effect in the solar wind-magnetosphere-ionosphere coupling.