Distribution characteristics of nighttime medium-scale traveling ionospheric disturbances (MSTIDs) over China and their connections with mid-latitude spread F

This study investigates the spatiotemporal characteristics of periodic TEC disturbances associated with medium-scale traveling ionospheric disturbances (MSTIDs) in the China sector and their statistical connection with midlatitude spread F (MSF). MSTIDs and MSF represent two of the most common phenomena at different scales in the midlatitude ionospheric F layer, exhibiting potential spatiotemporal connections. Utilizing data from over 250 GNSS stations of CMONOC and four ionosonde stations from CRIRP, we conduct a statistical analysis of the distribution patterns of MSTIDs activity during summer nights from 2014 to 2023 and their association with spread F phenomena. The results reveal the solar activity and seasonal dependence of MSTIDs in the Chinese sector—occurrence rates are significantly higher during solar minimum years than maximum years, with primary activity occurring during summer nights. Spatially, MSTIDs exhibit two peak occurrence regions driven by different mechanisms: the eastern peak aligns with characteristics driven by Perkins instability, while the western peak is closely associated with frequent gravity wave activity near southeast of the Tibetan Plateau. Further research indicates that MSTIDs and FSF tend to occur on the same night but maintain a stable statistical temporal sequence: MSTID activity precedes FSF occurrence. This chronological characteristic provides critical observational evidence for uncovering the potential triggering role of MSTIDs in FSF.