Collaborative Research: CEDAR--Interhemispheric Asymmetry of the Equatorial Ionization Anomaly in the American Sector

One of the interesting features of the Earth’s ionospheric F-region is the Equatorial Ionization Anomaly (EIA), which is characterized by low electron densities over the geomagnetic equator, while enhancements on either side of the equator. The presence and variability of the EIA significantly influences radio communication and navigation/positioning at low and middle latitudes, which are crucial to public safety and national security. Importantly, the EIA peaks often exhibit pronounced interhemispheric asymmetry (IHA), which can vary significantly over solar cycles or on a day-to-day basis. However, understanding the characteristics, formation mechanisms, and potential space weather effects of the variations in the IHA of the EIA across different timescales remains a poorly understood area. Addressing this knowledge gap is the primary goal of this project, aiming to enhance the predictions of the EIA variation and mitigations of the impacts on global communication and navigation systems. The project provides vital support and training for an early career researcher. Additionally, the research project will also serve as a cornerstone for the thesis work of a physics graduate student. This project aims to (a) to explore the variability of the IHA of the EIA in the American Sector across different solar cycles and elucidate its physical mechanisms, and (b) unravel the mechanisms driving the significant IHA of the post-sunset EIA in the American Sector and its correlation with scintillation activity during SSW events The methodology involves analyzing total electron content (TEC) data obtained from ground-based GNSS receivers distributed across the American Sector to examine the IHA's variability over multiple solar cycles. Additionally, the team will investigate the influence of lower atmospheric forcing on the IHA variations using NCAR TIEGCM simulations. The latter will be employed to investigate the formation of the significant IHA in the post- sunset EIA, while the GNSS measurements will be utilized to study the relationship between post-sunset IHA and scintillation occurrences. This project will significantly advance our understanding of the variability of the IHA of the EIA in the American Sector across different solar cycles. Moreover, it will shed light on the impact of the lower atmospheric forcings on the IHA of the EIA and its variability over solar cycles. Additionally, the study will provide valuable insights into the formation of the significant IHA of the post-sunset EIA and its linkage to the L-band scintillations during SSW events. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.