Magnetic reconnection and the Kelvin-Helmholtz instability in the solar corona
| Autor: | David Pontin, Ineke De Moortel, Thomas Howson |
|---|---|
| Přispěvatelé: | European Research Council, Science & Technology Facilities Council, University of St Andrews. Applied Mathematics, University of St Andrews. Office of the Principal |
| Rok vydání: | 2021 |
| Předmět: |
010504 meteorology & atmospheric sciences
media_common.quotation_subject T-NDAS FOS: Physical sciences Solar corona Astrophysics Public administration 01 natural sciences Helmholtz instability Excellence oscillations [MHD] 0103 physical sciences MHD waves and instabilities QB Astronomy media_common.cataloged_instance European union 010303 astronomy & astrophysics QC Solar and Stellar Astrophysics (astro-ph.SR) QB 0105 earth and related environmental sciences media_common Magnetohydrodyanmics (MHD) Physics Astronomy and Astrophysics Magnetic reconnection QC Physics Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science Research council Physics::Space Physics |
| Zdroj: | Astronomy & Astrophysics. 656:A112 |
| ISSN: | 1432-0746 0004-6361 |
| Popis: | Context. The magnetic Kelvin-Helmholtz instability (KHI) has been proposed as a means of generating magnetohy- drodynamic turbulence and encouraging wave energy dissipation in the solar corona, particularly within transversely oscillating loops. Aims. Our goal is to determine whether the KHI encourages magnetic reconnection in oscillating flux tubes in the solar corona. This will establish whether the instability enhances the dissipation rate of energy stored in the magnetic field. Methods. We conducted a series of three-dimensional magnetohydrodynamic simulations of the KHI excited by an oscillating velocity shear. We investigated the effects of numerical resolution, field line length, and background currents on the growth rate of the KHI and on the subsequent rate of magnetic reconnection. Results. The KHI is able to trigger magnetic reconnection in all cases, with the highest rates occurring during the initial growth phase. Reconnection is found to occur preferentially along the boundaries of Kelvin-Helmholtz vortices, where the shear in the velocity and magnetic fields is greatest. The estimated rate of reconnection is found to be lowest in simulations where the KHI growth rate is reduced. For example, this is the case for shorter field lines or due to shear in the background field. Conclusions. In non-ideal regimes, the onset of the instability causes the local reconnection of magnetic field lines and enhances the rate of coronal wave heating. However, we found that if the equilibrium magnetic field is sheared across the Kelvin-Helmholtz mixing layer, the instability does not significantly enhance the rate of reconnection of the background field, despite the free energy associated with the non-potential field. 17 pages, 19 figures |
| Databáze: | OpenAIRE |
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