The Role of the Fountain Effect in the Evolution of Ionospheric Structures in Low and Mid Latitudes

The Earth’s ionosphere is the layer of the atmosphere that has a relatively high concentration of charged particles (ions and free electrons) that extends from about 50 to 600 miles (80 to 1,000 km) above the Earth's surface. The density of the charged particles varies with location and time and is influenced by the change of Earth’s magnetic field.

These density fluctuations are called irregularities that affect radio communications and GPS accuracy. One special phenomenon is a regional depletion of charged particles (plasma), which is referred to as plasma bubbles.

This project is to perform a focused study of the daytime electron density irregularities during magnetically quiet periods and midlatitude plasma bubbles during magnetically disturbed periods in the low and mid latitude ionosphere. Both phenomena are believed to be closely related to equatorial plasma bubbles. The hypothesis is that both phenomena are closely related to the transport of equatorial bubbles by the fountain effect.

The success of this project will establish the full evolution scenario of equatorial bubbles throughout a day and provide closure to the dispute regarding the sources of midlatitude bubbles. The project team will establish the characteristics of daytime irregularities and midlatitude bubbles by analyzing satellite observations (ROCSAT-1, C/NOFS, CHAMP, SWARM, and DMSP).

The physical processes underlying these phenomena will be identified by conducting SAMI3 model simulations.

Both daytime irregularities and midlatitude bubbles are unexplored fields in that there is no clear knowledge of their characteristics and origin. Bubbles have been understood as the phenomena in the equatorial region, but anomalously large bubbles can develop and reach midlatitudes. This project is the first attempt to validate this interpretation by model simulations.

The proposed work is feasible because the project will be performed using existing observational data and a proven ionospheric model. The project team consists of experts in observational data, models, and ionospheric phenomena, and therefore, can effectively perform the project.

The Geospace & Earth Science group at Applied Physics Laboratory (APL) in Johns Hopkins University has been hosting high school and college interns so that they can participate in the staff’s projects. One college student will be invited in the summer to participate in this work and the team will provide mentoring on data analysis, computer programming, and ionospheric plasma physics.

This project will provide an opportunity to facilitate collaboration between APL and Korea Space science Institute (KASI) in space missions as well as ground-based observations through the collaboration with Dr. Wookyoung Lee at KASI. The project will also motivate other investigations of daytime irregularities in midlaittudes.

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.