Coronal hole boundaries evolution at small scales: I. EIT 195 A and TRACE 171 A view - Astrophysics > Solar and Stellar AstrophysicsReportar como inadecuado




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Abstract: We aim at studying the small-scale evolution at the boundaries of anequatorial coronal hole connected with a channel of open magnetic flux with thepolar region and an `isolated- one in the extreme-ultraviolet spectral range.We intend to determine the spatial and temporal scale of these changes. Imagerdata from TRACE in the Fe IX-X 171 A passband and EIT on-board Solar andHeliospheric Observatory in the Fe XII 195 A passband were analysed. We foundthat small-scale loops known as bright points play an essential role in coronalholes boundaries evolution at small scales. Their emergence and disappearancecontinuously expand or contract coronal holes. The changes appear to be randomon a time scale comparable with the lifetime of the loops seen at thesetemperatures. No signature was found for a major energy release during theevolution of the loops. Although coronal holes seem to maintain their generalshape during a few solar rotations, a closer look at their day-by-day and evenhour-by-hour evolution demonstrates a significant dynamics. The small-scaleloops 10- 40- and smaller which are abundant along coronal hole boundarieshave a contribution to the small-scale evolution of coronal holes. Continuousmagnetic reconnection of the open magnetic field lines of the coronal hole andthe closed field lines of the loops in the quiet Sun is more likely to takeplace.



Autor: M.S. Madjarska, T. Wiegelmann

Fuente: https://arxiv.org/







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