The ionized portion of the equatorial upper atmosphere exhibits significant variability from one day to the next. One important source of this day-to-day variability are plumes of plasma that contain complex - and poorly understood - internal structure that is collectively known as equatorial spread F (ESF). ESF is a complex phenomenon that involves a wide range of scales from equatorial plasma bubbles of tens of km in size to meter-scale irregularities in the plasma density. Recent results using ESF observations and numerical simulations suggested that ESF is difficult to predict by considering condition of the plasma (ionosphere) alone and that one reason may be different conditions in the neutral gas (thermosphere). In addition, vertical coupling between different altitudinal layers can be important in formation of plasma structures at various scales, and it has been previously suggested that metallic ions associated with meteoric deposition may be indirectly responsible for ESF. The goal of this research is to study thermospheric dynamics and metallic ions as possible causes of ESF. The global ionospheric model SAMI3 (Sami3 is Also a Model of the Ionosphere) will be further developed and complemented by a variety of models of thermospheric dynamics.

The work will involve (1) study of day-to-day variability of ESF by running the high-resolution version of SAMI3 for different thermospheric conditions as given by a variety of thermosphere models, (2) SAMI3 simulations of the effect of metallic ions (Fe+ and Mg+) on the onset and evolution of ESF through changing conductivity in the post-sunset ionosphere, and (3) further improvements in SAMI3 including implementing the 4th order partial donor cell transport scheme and the nested grid technique to achieve sufficiently high resolution without being computationally prohibitive.

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.