Optical flow analysis of the aurora borealis

• Published in: IEEE geoscience and remote sensing letters Vol. 3; no. 1; pp. 159 - 163
• Main Authors: Blixt, E.M., Semeter, J., Ivchenko, N.
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.01.2006; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acceleration; arcs; Atmosphere; Aurora borealis; Auroras; Computational fluid dynamics; Estimators; Feasibility; Image motion analysis; Image sequence analysis; Ionosphere; Magnetosphere; Motion estimation; optical flow; Plasma accelerators; robust statistics; Robustness; Stimulated emission; Turbulence; Wavelengths
• ISSN: 1545-598X; 1558-0571; 1558-0571
• DOI: 10.1109/LGRS.2005.860981

Optical observations of the aurora have traditionally focused on the structure, intensity, and wavelength of the emissions. But the apparent motion of auroral forms offers another important diagnostic tool for investigating this poorly understood phenomenon. Prior analyses of auroral motion have focused on tracing individual features. In this letter, we investigate the feasibility of deriving the entire two-dimensional velocity field automatically using robust optical flow estimation. The analysis is applied to two narrow-field video sequences. Both examples are rich in small-scale structure and motion, but appear very different to the eye. The robust optical flow estimator performed well for regions of dense turbulent motion, while sheared flow and flow which is perpendicular to image intensity gradients, was poorly resolved. The relative magnitude of the outliers provides a quantitative measure of the validity of the underlying flow model and, hence, a means of automatically differentiating among auroral forms with differing physical origins. The technique can be used to deduce ionospheric electric fields and neutral winds, and the flow fields yield important physical information about the generation mechanism.