Spatial characteristics of wave-like structures in diffuse aurora obtained using optical observations

• Published in: Annales geophysicae (1988) Vol. 30; no. 12; pp. 1693 - 1701
• Main Authors: AXELSSON, K, SERGIENKO, T, NILSSON, H, BRÄNDSTRÖM, U, EBIHARA, Y, ASAMURA, K, HIRAHARA, M
• Format: Journal Article
• Language: English
• Published: Göttingen Copernicus 14-12-2012; Copernicus GmbH; Copernicus Publications
• Subjects: Auroras; Conjugates; Diffusion; Earth, ocean, space; Electron precipitation; Exact sciences and technology; External geophysics; Fine structure; Imaging systems; Magnetosphere; Modulation; Particle precipitation; Physics of the ionosphere; Pitch angle; Rymdteknik; Space Technology; Whistlers; Data analysis; Magnetospheric physics (Auroral phenomena); time variations; Electron precipitation; Pitch angle; Convection flow; Ionosphere (Particle precipitation Wave-particle interactions); Statistical study; Loss cone; Whistler wave; Polar ionosphere; Fine structure; magnetosphere; Diffuse aurora; Optical observation; protons; spatial variations; Diffusion; Particle wave interaction; waveforms
• ISSN: 0992-7689; 1432-0576; 1432-0576
• DOI: 10.5194/angeo-30-1693-2012

We present the results of a statistical study using optical images from ALIS (Auroral Large Imaging System) to investigate the spatial and temporal variations of structures in diffuse aurora. Analysis of conjugate Reimei data shows that such fine structures are a result of modulation of high-energy precipitating electrons. Pitch angle diffusion into the loss cone due to interaction of whistler mode waves with plasma sheet electrons is the most feasible mechanism leading to high-energy electron precipitation. This suggests that the fine structure is an indication of modulations of the efficiency of the wave-particle interaction. The scale sizes and variations of these structures, mapped to the magnetosphere, can give us information about the characteristics of the modulating wave activity. We found the scale size of the auroral stripes and the spacing between them to be on average 13-14 km, which corresponds to 3-4 ion gyro radii for protons with an energy of 7 keV. The structures move southward with a speed close to zero in the plasma convection frame.