GEM: Modeling Ultra-Low-Frequency (ULF) Waves in the Near-Earth Magnetosphere

An outstanding question in space physics is how energy is transported throughout the near space environment. Radio waves at ultra-low frequencies (0.3-3 kHz) serve as both a transport mechanism for energy throughout the magnetosphere and ionosphere and an important diagnostic of the space plasma properties. This project creates a new physics-based model to better understand the dynamics of the near-Earth space environment. The broader impacts of this project include developing new models relevant to our understanding and prediction of space weather - a national priority set out in the National Space Weather Action Plan - and the training of a graduate student.

Ultra-low-frequency (ULF) waves play a major role in the transport of energy in the near-Earth regions of the magnetosphere. The research will involve the development of a magnetohydrodynamic (MHD) wave code and its application to several problems involving ULF waves in the magnetosphere. The primary focus will be on the application of this model to problems in magnetoseismology, using these waves as a diagnostic of the plasma distribution throughout the magnetosphere. This can be accomplished both by a study of the properties of field line resonances as well as through the travel times of ULF waves from an impulsive source. While previous versions of the wave code have either been two-dimensional, or three-dimensional but with azimuthal symmetry, the code now allows for local time dependence of the ionosphere and plasmasphere. This allows for studies of the day-night differences in the ionosphere as well as the role of conductivity enhancements, such as in the auroral zone, or depletions, as can occur in the sub-auroral plasma trough. Including plasmaspheric asymmetry will allow for the dawn-dusk differences in the plasmasphere structure, including the possible presence of plasmaspheric plumes. Development and application of a global ULF wave model that can investigate these interactions is the primary goal of the research.

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.