Multi-Scale Experimental Investigations of Extreme Plasma Density Depletions in the Polar Ionosphere

Atmospheric & Space Technology Research Associates, L.L.C., Louisville CO

Investigators

Abstract

This project will investigate a phenomenon called ‘polar holes’ in the polar ionosphere, which is a region of atmosphere (80 to 1000 km above sea level) that is highly ionized due to solar radiation, with high concentration of charged particles, i.e. electrons and ions. The polar hole refers to the large reduction of charged particles (called plasma) that appears from time to time in the so-called F-region (150 to 500 km) and is believed to happen more often during the solar minimum when the solar radiation is at its lowest level. The formation of such holes is related to the complex interactions of the charged particles with the electromagnetic field and atmospheric circulation that are unique in the polar region. Understanding the formation and internal structures of the polar holes fills the gap of our understanding of such interactions and helps improve model simulation of the polar ionosphere. The current solar minimum provides a good opportunity to study this phenomenon. This project will experimentally investigate the polar holes and the role of the plasma convection in their formation and evolution. Polar holes are believed to be formed during the periods of the very slow anti-sunward convection, when the plasma is trapped just poleward of the statistical auroral oval in the absence of any ionization sources. At the same time, fast convection with rapid vertical plasma transport has also been associated with the polar hole formation. Combining the multi-point capability of the Advanced Modular Incoherent Scatter Radar (AMISR) located in the northern polar cap, the state of art variational data assimilation tool IDA4D developed at ASTRA, and the convection data from the Super Dual Auroral Radar Network (SuperDARN) array, the role of plasma convection in the polar hole formation will be investigated. The density in the vicinity of the polar holes is thought to be very structured. This study will explore the polar hole internal structure, analyze the gradients that are present inside the polar hole and on its edges, and evaluate their effects on high-frequency radar backscatter. Finally, to improve the predictability of the electron density conditions in polar cap regions, which are most problematic for modeling, a statistical analysis of the polar cap density during the solar minimum conditions will be performed. Variability of the polar cap density will be investigated using IDA4D runs and large amounts of collected radio occultation data from COSMIC I mission in the northern and southern polar regions to find the most problematic time periods where the model parameters and data-derived parameters have the largest differences. The work will improve our knowledge of the plasma depletions in the polar cap during solar minimum conditions. The polar cap during the winter and during the solar minimum is one of the most problematic zones for the ionospheric models used in application areas, such as satellite communications, satellite-based navigation, data links, and space situational awareness. This work will improve the ability to model the electron density in the polar cap region by direct investigation of its lowest extremes and by statistical investigation of its variability. This project will support an early-career female researcher who has a strong track record of outreach activities, including delivering Space Physics lectures for senior people and developing the www.sheisaphysicist.com web space that promotes and cultivates the success of women in physics by publishing stories about the career path of female physicists. When a new interview is published, the website reaches ~2000 independent views, inspiring high-school and undergraduate female students to choose physics as their career path. This will contribute to broadening of participation of underrepresented minorities in STEM fields. 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.