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Three-dimensional magnetic field topology in a region of solar coronal heating


Flares and X-ray jets on the Sun arise in active regions where magnetic flux emerges from the solar interior amd interacts with the ambient magnetic field1,2. The interactions are believed to occur in electric current sheets separating regions of opposite magnetic polarity. The current sheets located in the corona or upper chromosphere have long been thought to act as an important source of coronal heating3,4,5,6, requiring their location in the corona or upper chromosphere. The dynamics and energetics of these sheets are governed by a complex magnetic field structure that, until now, has been difficult to measure. Here we report the determination of the full magnetic vector in an interaction region near the base of the solar corona. The observations reveal two magnetic features that characterize young active regions on the Sun: a set of rising magnetic loops and a tangential discontinuity of the magnetic field direction, the latter being the observational signature of an electric current sheet. This provides strong support for coronal heating models based on the dissipation of magnetic energy at current sheets.

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Figure 1: Atmospheric parameters of an emerging flux region (NOAA active region 9451, 33°W, 22°S).
Figure 2: Magnetic and velocity field parameters obtained from the He triplet along ‘Cut 1’ in Fig. 1.
Figure 3: Reconstructed magnetic loops in the emerging flux region.
Figure 4: Representation of the electric current sheet (See ‘Region 2’ in Fig. 1 for the location within the full scanned region).


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M.C. acknowledges support from the Spanish Ministerio de Ciencia y Tecnologia. We thank the Kiepenheuer Institut in Freiburg, Germany, for observing support.

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Correspondence to S. K. Solanki.

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Solanki, S., Lagg, A., Woch, J. et al. Three-dimensional magnetic field topology in a region of solar coronal heating. Nature 425, 692–695 (2003).

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