Heating of the solar chromosphere in a sunspot light bridge by electric currents
| Autor: | Christian Beck, Mehmet Sarp Yalim, Avijeet Prasad, Rohan E. Louis, Debi Prasad Choudhary |
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| Rok vydání: | 2021 |
| Předmět: |
010504 meteorology & atmospheric sciences
Field (physics) Thermodynamic equilibrium FOS: Physical sciences Astrophysics 01 natural sciences 7. Clean energy 0103 physical sciences Thermal Astrophysics::Solar and Stellar Astrophysics 010303 astronomy & astrophysics Chromosphere Solar and Stellar Astrophysics (astro-ph.SR) 0105 earth and related environmental sciences Physics Sunspot Photosphere Astronomy and Astrophysics Computational physics Magnetic field Astrophysics - Solar and Stellar Astrophysics 13. Climate action Space and Planetary Science Physics::Space Physics Astrophysics::Earth and Planetary Astrophysics Electric current |
| DOI: | 10.48550/arxiv.2107.12066 |
| Popis: | Context: Resistive Ohmic dissipation has been suggested as a mechanism for heating the solar chromosphere, but few studies have established this association. Aim: We aim to determine how Ohmic dissipation by electric currents can heat the solar chromosphere. Methods: We combine high-resolution spectroscopic Ca II data from the Dunn Solar Telescope and vector magnetic field observations from the Helioseismic and Magnetic Imager (HMI) to investigate thermal enhancements in a sunspot light bridge. The photospheric magnetic field from HMI was extrapolated to the corona using a non-force-free field technique that provided the three-dimensional distribution of electric currents, while an inversion of the chromospheric Ca II line with a local thermodynamic equilibrium and a nonlocal thermodynamic equilibrium spectral archive delivered the temperature stratifications from the photosphere to the chromosphere. Results: We find that the light bridge is a site of strong electric currents, of about 0.3 A/m^2 at the bottom boundary, which extend to about 0.7 Mm while decreasing monotonically with height. These currents produce a chromospheric temperature excess of about 600-800 K relative to the umbra. Only the light bridge, where relatively weak and highly inclined magnetic fields emerge over a duration of 13 hr, shows a spatial coincidence of thermal enhancements and electric currents. The temperature enhancements and the Cowling heating are primarily confined to a height range of 0.4-0.7 Mm above the light bridge. The corresponding increase in internal energy of 200 J/m^3 can be supplied by the heating in about 10 min. Conclusions: Our results provide direct evidence for currents heating the lower solar chromosphere through Ohmic dissipation. Comment: Accepted for publication in Astronomy & Astrophysics Letters: 7 pages, 5 figures |
| Databáze: | OpenAIRE |
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