ANGEO Annales Geophysicae ANGEO Ann. Geophys. 1432-0576 Springer Verlag Göttingen, Germany 10.1007/s00585-996-1257-2 Auroral-arc splitting by intrusion of a new convection channel Frey H. U. 1 Haerendel G. 1 Buchert S. 2 Lanchester B. S. 3 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstr., D-85740 Garching, Germany Institut für Geophysik und Meteorologie, TU Braunschweig, Mendelssohnstr. 3, D-38106 Braunschweig, Germany University of Southampton, Department of Physics, Southampton, SO17 1BJ, UK 31 12 1996 14 12 1257 1264 Copyright: © 1996 H. U. Frey et al. 1996 © European Geosciences Union 1996 This article is available from https://angeo.copernicus.org/articles/14/1257/1996/angeo-14-1257-1996.html The full text article is available as a PDF file from https://angeo.copernicus.org/articles/14/1257/1996/angeo-14-1257-1996.pdf

During a run of the Common Programme Three of the EISCAT radar the splitting of an auroral arc was observed by high time-resolution, ground-based cameras when the UHF radar beam was close to the arc. The evening eastward electrojet situation with a large-scale northward ionospheric electric field was disturbed by the intrusion of a convection channel with southward electric field from the east. The interaction of the new convection channel with the auroral arc caused changes in arc brightness and arc splitting, i.e. the creation of a new arc parallel to the pre-existing auroral arc. The event is described as one possibility for the creation of parallel arcs during slightly disturbed magnetic conditions far from the Harang discontinuity.