Structure and Evolution of Dayside Diffuse Aurora and Enhanced Magnetospheric Density Regions from Coordinated Observations of South Pole All-Sky Imager and THEMIS Spacecraft

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

Plasma density is one of the fundamental quantities of the magnetosphere-ionosphere (M-I) coupling that affects the growth and propagation of various plasma wave modes, magnetic reconnection rate, and ionospheric conductance; all of which strongly influence energy and mass transport in the M-I system. By taking advantage of simultaneous satellite-ground conjunctions in recent years, this award will help determining the source region of dayside density modulations, specifically addressing three outstanding scientific questions: Where does the enhanced density originate? How do enhanced density regions evolve in time? And what is the typical size of the enhanced density regions? The plasma density in the dayside magnetosphere is highly structured, and this structure can have a large impact on the excitation of whistler-mode waves that in turn scatter plasma sheet electrons drifting from the nightside and accelerate electrons in the Earth's radiation belts. It has been recently found that whistler-mode waves drive structured patches of the diffuse aurora; this can be used to highlight enhanced density regions in the dayside magnetosphere. The dayside 'aurora-wave-density' correlations lead to questions about the origin of enhanced plasma density patches and their propagation in the dayside magnetosphere. Satellite observations alone have difficulties separating spatial and temporal effects in tracing the motion of enhanced density regions, but ground-based 2D auroral imaging could offer an excellent technique for monitoring the shape and motion of diffuse aurora that is driven by precipitating energetic electrons interacting with whistler-mode waves. The proposed investigation will use a creative approach for understanding dayside magnetospheric density evolution by using Antarctic-based auroral observations. In particular, South Pole is an ideal dayside auroral observatory due to its longest polar night in the world. The wave-particle interaction producing whistler-mode waves will be used as a tool for imaging dayside plasma density structures using correlated South Pole all-sky auroral imager and THEMIS spacecraft observations. This research may influence not only its own field of diffuse auroral studies, but also related fields such as dayside magnetospheric dynamics, wave particle interactions, and excitation of plasma waves. This interesting and important scientific research provides an ideal opportunity to train a graduate student, further scientific collaboration and cooperation in Antarctica, and create a list of THEMIS-South Pole auroral imager 'dayside conjunction' events and respective geomagnetic field mapping results for the use by a broader geospace science community.