Measurement of coronal magnetic twists during loop emergence of NOAA 8069
Delaboudinière, J. -P.; Démoulin, P.; Portier-Fozzani, F.; Aschwanden, M.; Neupert, W.; EIT Team
Germany, United States, France
Abstract
Emerging coronal loops were studied with extreme ultraviolet observations performed by SOHO/EIT on 5 and 6 August 1997 for NOAA 8069. Physical parameters (size and twist) were determined by a new stereoscopic method. The flux tubes were measured twisted when first observed by EIT. After emerging, they de-twisted as they expanded, which corresponds to a minimization of the energy. Different scenarios which take into account the conservation of the magnetic helicity are discussed in relation with structure and temperature variations.