Does bursty bulk flow affect F-region irregularities in the auroral ionosphere?

In this paper, we investigate the relationship between bursty bulk flows (BBFs) in the magnetotail and ionospheric irregularities at Swarm altitude in the nightside auroral ionosphere. A database of 487 BBF-Swarm conjunction events during 2017-2024 is constructed by mapping BBFs to the ionosphere using Tsyganenko magnetic field models and selecting Swarm passes within 200 km and 15 min of the mapped BBF centroids. We make use of relevant Swarm datasets, including plasma density, temperature, density fluctuations and gradients at multiple scales, field-aligned currents (FACs), and cross-track ion velocities. Two case studies in the Northern and Southern Hemispheres show that BBFs can coincide with enhanced FACs, strong and rapidly varying ion flows, and intensified F-region ionospheric irregularities. However, enhanced F-region irregularities can also occur outside of the BBF conjunction time. Before presenting the statistical study, we show that ionospheric irregularities are highly variable and depend on solar and geomagnetic activity, local time, and season. The statistical comparison of upper-quartile F-region irregularity parameters near BBFs with the surrounding nightside auroral region shows only negligible differences. However, there are also large extreme values of differences between BBF and background, where the BBF intervals show clear enhancement of more than 100%. We further conduct a superposed epoch analysis. Though the analysis shows that BBFs have a clear FAC signature, there is no distinct enhancement of F-region irregularity indices near BBFs as compared to the nightside auroral region. These results suggest that while BBFs can locally generate or intensify F-region irregularities, their statistical impact is not stronger than that of other auroral processes. Uncertainties in BBF footpoint mapping, limitations in auroral region identification, uneven sampling over the solar cycle, season, and longitude, and the presence of multiple unresolved BBFs and auroral structures likely contribute to the weak statistical signature. Overall, BBFs are one of several contributors to F-region irregularities at auroral latitudes, but their effect cannot be uniquely isolated from the general nightside auroral environment in F-region irregularities observed by Swarm.