Collaborative Research: Effects of Thermospheric Winds on Equatorial Spread-F

The Earth’s ionosphere is a layer of atmosphere starting at about 50 miles above the surface of the Earth with relatively high concentration of charged particles. Long-distance radio communications on Earth rely on reflection of radio waves by this layer; communications between satellites and ground stations rely on radio waves passing through this layer.

The quality of such radio communications highly depends on density of charged particles in the ionosphere. When there is large variation of the density, radio wave propagation could be disrupted. One such large density variation at low latitudes is known as equatorial plasma bubbles (EPBs), which are often created under the combined influence of diurnal change of solar radiation and the atmosphere wind.

How these bubbles are related to the change of atmospheric wind is a fundamental science question and its understanding could lead to better prediction of when and where these bubbles may form and help to mitigate the interruptions they create.

The purpose of this project is to employ observations and modeling to investigate the relationship between thermospheric neutral winds and equatorial spread F (ESF), which is a manifestation of bubbles when detected by radars. The fundamental science question to be addressed is: How does the day-to-day variability of neutral winds contribute to the onset and evolution of EPBs?

A multi-year observational data of concurrent thermospheric neutral winds and EPBs in the low latitudes will be developed and used to determine the relationships between winds and ESF/scintillation. The data will enable monitoring of the development and evolution of ESF and provide a deep insight into both the short-term (hourly, diurnal) and long-term (seasonal) processes and the underlying physics.

Additionally, the SAMI3 (Sami3 is Also a Model of the Ionosphere) ionosphere model will be used to capture the ionospheric dynamics associated with different thermospheric conditions, to allow determination of how various scenarios give rise to EPBs/ESF and how they evolve over short (diurnal) and long (seasonal) time periods. The SAMI3 model is comprehensive and capable of addressing important problems in aeronomy that are not accessible with other models.

The combination of the data and modeling will lead to a fundamentally deeper understanding of the dynamical processes underlying EPBs and ESF.

Over the long term, the ground-based neutral wind observations could be used to forecast the likelihood of ESF and predict the onset of scintillation and characterize its evolution with time. Being able to predict and characterize ESF/scintillation from ground-based sensors is critical for operational civilian and national security purposes. Scintillation affects trans-ionospheric radio signals up to a few GHz in frequency and as such can have detrimental impacts on systems such as:

a) Satellite-based systems that are used for communications, positioning, navigation and timing. b) Both civil and national security vertical and oblique (over the horizon) radar systems. c) Scientific instruments requiring observations of trans-ionospheric radio signals (e.g., radio astronomy).

All the software and data from this research will be made publicly available. Support will be provided to students and academics who may want to reproduce and advance the findings using the models and the datasets. JHU/APL will provide in-house participation of high-school, undergraduate, and graduate students to help them get research, education, and professional development experience.

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.