[P-EM12] Coupling Processes in the Atmosphere-Ionosphere System

[PEM12-27] Investigation of the Local Time Dependence of Post-Sunset Medium-Scale Traveling Ionospheric Disturbances Over Japan

*Weizheng Fu¹, Yuichi Otsuka¹ (1.Institute for Space-Earth Environmental Research, Nagoya University )

Keywords:MSTID, GNSS-TEC, Ionospheric irregularity

Ionospheric irregularities have extensively been an intriguing subject of research. Medium-scale traveling ionospheric disturbances (MSTIDs) serve as a common and significant manifestation of ionospheric perturbations predominantly observed in midlatitude regions. Particularly during nighttime, MSTIDs commonly exhibit a preference for a northwest-southeast (NW-SE) (northeast-southwest; NE-SW) alignment in the Northern (Southern) Hemisphere. Although the prevailing theory on the generation of nighttime MSTID is the E-F coupling, the limited observation coverage or spatiotemporal resolution inherent in many observational techniques prevent us from gaining a deeper understanding of this intricate process. In this research, we focus on the transition period when nighttime MSTIDs begin to generate. Dense GNSS observations from GEONET and SoftBank networks over Japan, complemented by multi-source data from other ground- and space-based ionosphere sounding techniques, are used to provide valuable insights into the MSTID generation, development, and persistence. In addition to the 2-D analysis, a 3-D tomography technique has been developed to analyze the structure variations of post-sunset MSTIDs. Preliminary findings indicate a clear correlation between local time and MSTID development after sunset. The complex interactions between the atmosphere and ionosphere could be important for comprehending the post-sunset MSTIDs.

Acknowledgements
The authors thank GSI and SoftBank Corp. and ALES Corp. for providing the GNSS RINEX files.