Collaborative Research: Characterizing the Quiet Time Equatorial Plasma Bubbles

The objective of this project is to characterize quiet-time equatorial plasma bubbles that induce scintillation on radio signals. Radio signal scintillation poses a significant space weather threat, impacting various agencies reliant on GNSS and VHF/HF radio signal applications. These include government entities such as the DoD (e.g., for RF surveillance and first responders), the FAA’s wide-area augmentations system (WAAS) that is currently in use by commercial air travel, the DoA (e.g., for precision farming), the DoT (e.g., for land surveying, mining, and highway maintenance), and many others. The successful completion of the project will contribute improving ionospheric specification and forecasting, thereby bolstering the reliability of communication and navigation systems operating across a wide spectrum of frequencies, from HF to L-band. This is critically important for numerous societal applications that necessitate continuous access to ultra-precise location data. Furthermore, the project aims to support students in STEM fields, and facilitate training of early career scientists and summer students. This aligns well with one of NSF’s missions: “to promote the progress of science; to advance the national health, prosperity and welfare; or to secure the national defense”. The occurrence of equatorial plasma bubbles (EPBs) that causes scintillation in the low-latitude region is not solely dictated by storm-time conditions or the presence of a significant pre-reversal enhancement (PRE) vertical drift. Recent observations indicate that the forcing from below, such as gravity waves (GWs), propagates upward, seeding the bottom side ionosphere and triggering sequences of EPBs during magnetically quiet periods, affecting radio signal operations at low latitudes. The scope of the project is to characterize magnetically quiet time EPBs, investigate their driving mechanisms, and address three fundamental questions: (SQ1) What drives the quiet time EPBs? Is it due to the bottom side seeding initiated by the forcing from a lower atmosphere or to RTI triggered by strong vertical drift? (SQ2) Which driving mechanism primarily governs the pronounced longitudinal, day-to-day, and seasonal dependences of the quiet time EPBs? (SQ3) What specific parameters control the dynamics and lifetime of EPBs, as well as the scale and intensity of scintillations during their presence? The project will encompass various case studies at different locations and local times, as well as statistical analyses based on measurements carried out since 2008. The project will leverage data from a multitude of instruments, including GNSS receivers, instruments onboard various LEO satellites, VIPIR ionosonde networks, and GOLD UV images, TIMED datasets. Utilization of SAMI3 model is planned with inputs informed through observations is envisioned to comprehend and advance the scientific knowledge about EPB evolution process. 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.