Magnetic flux emerges from the solar surface as dark filaments connecting small sunspots with opposite polarities1,2,3. The regions around the dark filaments are often bright in X-rays and are associated with jets4,5,6. This implies plasma heating and acceleration, which are important for coronal heating. Previous two-dimensional simulations of such regions showed that magnetic reconnection between the coronal magnetic field and the emerging flux produced X-ray jets and flares, but left unresolved the origin of filamentary structure and the intermittent nature of the heating. Here we report three-dimensional simulations of emerging flux showing that the filamentary structure arises spontaneously from the magnetic Rayleigh–Taylor instability7,8, contrary to the previous view that the dark filaments are isolated bundles of magnetic field that rise from the photosphere carrying the dense gas9,10,11. As a result of the magnetic Rayleigh–Taylor instability, thin current sheets are formed in the emerging flux, and magnetic reconnection occurs between emerging flux and the pre-existing coronal field in a spatially intermittent way. This explains naturally the intermittent nature of coronal heating and the patchy brightenings in solar flares.
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The authors thank N. O. Weiss, A. Asai and D. H. Brooks for comments. Use of TRACE data is acknowledged. This work was supported by the Japan–UK Cooperation Science Program of the JSPS (Principal investigators K.S. and N. O. Weiss) and a Grant-in-Aid for the 21st Century COE ‘Centre for Diversity and Universality in Physics’ from MEXT, Japan. The numerical computation was performed on the Earth Simulator.
The authors declare that they have no competing financial interests.
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Isobe, H., Miyagoshi, T., Shibata, K. et al. Filamentary structure on the Sun from the magnetic Rayleigh–Taylor instability. Nature 434, 478–481 (2005). https://doi.org/10.1038/nature03399
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