How is helicity (and twist) partitioned in magnetohydrodynamic simulations of reconnecting magnetic flux tubes?
| Autor: | Andrew N. Wright, A. W. Hood, J. Threlfall |
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| Přispěvatelé: | Science & Technology Facilities Council, University of St Andrews. Applied Mathematics |
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Physics
T-NDAS Magnetohydrodynamical simulations Astronomy and Astrophysics Helicity Magnetic flux Magnetic field Solar magnetic reconnection Magnetohydrodynamics QC Physics Space and Planetary Science Quantum electrodynamics Magnetic fields Physics::Space Physics Astrophysics::Solar and Stellar Astrophysics QB Astronomy Magnetohydrodynamic drive Twist QC QB |
| Popis: | Funding: STFC through the Consolidated grant, ST/N000609/1, to the University of St Andrews. Magnetic helicity conservation provides a convenient way to analyze specific properties (namely, the linkage and twist) of reconnecting flux tubes and yield additional insight into the pre- and post-reconnection states of magnetic structures in the solar atmosphere. A previous study considered two flux tubes with footpoints anchored in two parallel planes. They showed that reconnection would add self-helicity equivalent to a half turn of twist to each flux tube. We address a related and fundamental question here: if two flux tubes anchored in a single plane reconnect, what are the resulting twists imparted to each of the reconnected tubes? Are they equal and do they have a simple exact value independent of footpoint location? To do this, we employ a new (computationally efficient) method which subdivides each flux tube into distinct elements and calculates the mutual helicity of many elemental pairs, the sum of which determines the self-helicity of the overall flux tube. Having tested the method using a simple analytical model, we apply the technique to a magnetohydrodynamic simulation where initially untwisted magnetic flux tubes are sheared and allowed to reconnect (based on a previous reconnection model). We recover values of self-helicity and twist in the final end state of the simulations which show excellent agreement with theoretical predictions. Publisher PDF |
| Databáze: | OpenAIRE |
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