3/10/2023 0 Comments Sun corona energy outputMany such heating events could be capable of heating the corona to the observed temperatures. The reconnection of braided field lines is thought to lead to small, impulsive heating events with energies of 10 24 erg, the so-called nanoflares ( Parker 1972, 1983, 1988). In the direct current (DC) model, small-scale horizontal photospheric motions at the loop footpoints lead to tangling of the magnetic field lines. 2021) and the braiding of the magnetic field lines by photospheric motions ( Parker 1972, 1983, 1988 Priest et al. 2011, 2014 Parnell & De Moortel 2012 Shi et al. Proposed models include wave heating ( Alfvén 1947 van Ballegooijen et al. The heating mechanism that sustains coronal loops is subject to active discussions. The plasma temperatures in the coronal loops range from 1 to about 10 MK. Coronal loops can be found in the quiet sun as well as in active regions. Solar coronal loops are bright structures of hot plasma confined by the magnetic field, observable in X-ray and extreme ultraviolet (EUV) light ( Reale 2014). Open Access funding provided by Max Planck Society. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License ( ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. With this model we can build a coherent picture of how the energy flux to heat the upper atmosphere is generated near the solar surface and how this process drives and governs the heating and dynamics of a coronal loop. Overall, our model roughly reproduces the properties and evolution of the plasma as observed within (the substructures of) coronal loops.Ĭonclusions. The synthesized emission, as it would be observed by the Atmospheric Imaging Assembly or the X-Ray Telescope, reveals transient bright strands that form in response to the heating events. We see little sign of heating by large-scale braiding of magnetic flux tubes from different photospheric concentrations at a given footpoint. Turbulence develops in the upper layers of the atmosphere as a response to the footpoint motions. The loop is heated by a Poynting flux that is self-consistently generated through small-scale motions within individual magnetic concentrations in the photosphere. The footpoints were allowed to interact self-consistently with the granulation surrounding them. Field-aligned heat conduction, gray radiative transfer in the photosphere and chromosphere, and optically thin radiative losses in the corona were taken into account. To resolve its internal structure, we limited the computational domain to a rectangular box containing a single coronal loop as a straightened magnetic flux tube. In a 3D magnetohydrodynamics model, we study an isolated coronal loop rooted with both footpoints in a shallow layer within the convection zone using the MURaM code. Here we investigate how the energy to heat the loop is generated by photospheric magneto-convection, transported into the upper atmosphere, and how the internal structure of a coronal magnetic loop forms. Comprehending how these are energized, structured, and evolve is key to understanding stellar coronae.Īims. Coronal loops are the basic building block of the upper solar atmosphere as seen in the extreme UV and X-rays. High Altitude Observatory, NCAR, PO Box 3000 Boulder, CO 80307, USAĬontext. Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, GermanyĮ-mail: of Space Research, Kyung Hee University, Yongin, Gyeonggi 446-701, Republic of Korea
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