Phase Coherence in Elemental Auroral Structure

Trustees Of Boston University, Boston

Investigators

Abstract

This is a three-year research project concerning the physics of dynamic discrete aurora, generally associated with geomagnetic substorms and storms. The specific overarching goal is to determine the extent to which elemental (sub-100-meter) structure in the discrete aurora is consistent with field and particle configurations of dispersive Alfven waves. The work will utilize two observational innovations. The first is the use a new narrow-field high-speed imaging system based on Electron Multiplying CCD (EMCCD) technology. This will make it possible to quantify phase coherence in fine-scale auroral structure in space and time at unprecedented resolution. Additional data for this research will be provided by a new permanent EMCCD imaging system that is being established at Poker Flat. The second innovation is the use of the high-speed steering capabilities of the Poker Flat IS radar (PFISR) to identify regions of coherent scatter associated with filamentary (Alfvenic) current systems at <1 s cadence. These local measurements will be placed in a global-scale context using multi-station observations from the THEMIS all-sky camera array, as well as measurements of the auroral power source from the THEMIS satellites themselves. A comprehensive program combining unique observational capabilities, the development of sophisticated new analysis tools, modeling, and theoretical interpretation will be conducted to address three specific questions: 1) Can wave dispersion account for spatiotemporal variability in observed precipitation patterns? 2) Is there evidence for multiple reflections (resonant modes), or can all fine-scale structure be accounted for by direct absorption of wave energy? 3) Is more than one fundamental mechanism required to account for all elemental structure in the aurora? The project has significant broader impacts. Scientifically, the processes investigated in this project are fundamental to our general understanding of multi-scale energy balance in the high-latitude magnetosphere. The processes are also not unique to the terrestrial magnetospheric plasma; the insight gained in this research will inform our general understanding of energy transfer in cosmic and laboratory plasmas. Educationally, it will contribute to the training of two PhD scientists in the areas of auroral physics and image processing. Finally, the work will produce fascinating imagery of the aurora that will be utilized in public outreach efforts and shared widely over the web.