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Abstract: With the recent launch of the Hinode satellite our view of the nature andevolution of quiet-Sun regions has been improved. In light of the new highresolution observations, we revisit the study of the quiet Sun-s topologicalnature. Topology is a tool to explain the complexity of the magnetic field, theoccurrence of reconnection processes, and the heating of the corona. ThisLetter aims to give new insights to these different topics. Using ahigh-resolution Hinode-SOT observation of the line-of-sight magnetic field onthe photosphere, we calculate the three dimensional magnetic field in theregion above assuming a potential field. From the 3D field, we determine theexistence of null points in the magnetic configuration. From this model of acontinuous field, we find that the distribution of null points with height issignificantly different from that reported in previous studies. In particular,the null points are mainly located above the bottom boundary layer in thephotosphere 54% and in the chromosphere 44% with only a few null points inthe corona 2%. The density of null points expressed as the ratio of thenumber of null points to the number of photospheric magnetic fragments in thesolar atmosphere is estimated to be between 3% and 8% depending on the methodused to identify the number of magnetic fragments in the observed photosphere.This study reveals that the heating of the corona by magnetic reconnection atcoronal null points is unlikely. Our findings do not rule out the heating ofthe corona at other topological features. We also report the topologicalcomplexity of the chromosphere as strongly suggested by recent observationsfrom Hinode-SOT.



Autor: S. Regnier, C. E. Parnell, A. L. Haynes

Fuente: https://arxiv.org/







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