Relationship between supergranulation flows, magnetic cancellation and network flares
| Autor: | Davina Innes, Karl-Heinz Glassmeier, Sami K. Solanki, R. Attie |
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| Rok vydání: | 2016 |
| Předmět: |
Physics
Photosphere 010504 meteorology & atmospheric sciences Magnetic energy business.industry Astrophysics::High Energy Astrophysical Phenomena FOS: Physical sciences Astronomy and Astrophysics Astrophysics Plasma Dissipation 01 natural sciences Magnetic flux Magnetic field Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science Physics::Space Physics 0103 physical sciences Astrophysics::Solar and Stellar Astrophysics Supergranulation business 010303 astronomy & astrophysics Solar and Stellar Astrophysics (astro-ph.SR) Thermal energy 0105 earth and related environmental sciences |
| Zdroj: | Astronomy & Astrophysics. 596:A15 |
| ISSN: | 1432-0746 0004-6361 |
| Popis: | Context. Photospheric flows create a network of often mixed-polarity magnetic field in the quiet Sun, where small-scale eruptions and network flares are commonly seen.Aims. The aim of this paper is (1) to describe the characteristics of the flows that lead to these energy releases, (2) to quantify the energy build up due to photospheric flows acting on the magnetic field, and (3) to assess its contribution to the energy of small-scale, short-lived X-ray flares in the quiet Sun. Methods. We used photospheric and X-ray data from the SoHO and Hinode spacecraft combined with tracking algorithms to analyse the evolution of five network flares. The energy of the X-ray emitting thermal plasma is compared with an estimate of the energy built up due to converging and sheared flux.Results. Quiet-Sun network flares occur above sites of converging opposite-polarity magnetic flux that are often found on the outskirts of network cell junctions, sometimes with observable vortex-like motion. In all studied flares the thermal energy was more than an order of magnitude higher than the magnetic free energy of the converging flux model. The energy in the sheared field was always higher than in the converging flux but still lower than the thermal energy.Conclusions. X-ray network flares occur at sites of magnetic energy dissipation. The energy is probably built up by supergranular flows causing systematic shearing of the magnetic field. This process appears more efficient near the junction of the network lanes. Since this work relies on 11 case studies, our results call for a follow-up statistical analysis to test our hypothesis throughout the quiet Sun. |
| Databáze: | OpenAIRE |
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