In the light of the aurora

Optical auroral research in northernmost Europe

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The aurora, or northern lights, is the most variable light phenomenon in the sky and the result of physical processes taking place in near-Earth space. The colours, shapes, intensities, locations and movements of auroral forms give us information about these processes. Ground-based optical studies are superior for high-resolution measurements and to distinguish temporal and spatial effects. Arctic Europe is a most convenient place to study the aurora. Many instruments and research facilities have been placed here. The Network for Groundbased Optical Auroral Research in the Arctic Region is supported by the Nordic Council of Ministers and consists of all research institutions in northern Norway, Sweden, Finland and on theKola Peninsula active in optical auroral research. This reportintroduces optical aurora and optical research methods, research institutions and research infrastructure. It also describes the activities of the network: workshops, mobility programme and scientific results.



Research projects conducted within the network, descriptions and first results

Quasi-periodic deformations of auroral arcs have long been observed and categorized into spirals, folds and curls. Spirals appear on the largest scale with a diameter of the order of 100 km and they appear typically during an auroral substorm. Folds are loops in the arc with a diameter of about 20 km. Curls are the smallest scale distortions (1–10 km) described hitherto with a counter-clockwise rotational sense when viewed from the ground in the northern hemisphere. They manifest themselves as a series of vortices, most often in motion along the arc. It is commonly assumed that the curls are produced by the Kelvin-Helmholz instability driven by magnetospheric flow shear across the sheet of electrons producing aurora.


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