Sustained Heating of the Chromosphere and Transition Region Over a Sunspot Light Bridge
Sunspot light bridges (LBs) exhibit a wide range of short-lived phenomena in the chromosphere and transition region. In contrast, we use here data from the Multi-Application Solar Telescope (MAST), the Interface Region Imaging Spectrograph (IRIS), Hinode, the Atmospheric Imaging Assembly (AIA), and...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/aca612 |
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| author | Rohan E. Louis Shibu K. Mathew A. Raja Bayanna Christian Beck Debi P. Choudhary |
| author_facet | Rohan E. Louis Shibu K. Mathew A. Raja Bayanna Christian Beck Debi P. Choudhary |
| author_sort | Rohan E. Louis |
| collection | DOAJ |
| description | Sunspot light bridges (LBs) exhibit a wide range of short-lived phenomena in the chromosphere and transition region. In contrast, we use here data from the Multi-Application Solar Telescope (MAST), the Interface Region Imaging Spectrograph (IRIS), Hinode, the Atmospheric Imaging Assembly (AIA), and the Helioseismic and Magnetic Imager (HMI) to analyze the sustained heating over days in an LB in a regular sunspot. Chromospheric temperatures were retrieved from the MAST Ca ii and IRIS Mg ii lines by nonlocal thermodynamic equilibrium inversions. Line widths, Doppler shifts, and intensities were derived from the IRIS lines using Gaussian fits. Coronal temperatures were estimated through the differential emission measure, while the coronal magnetic field was obtained from an extrapolation of the HMI vector field. At the photosphere, the LB exhibits a granular morphology with field strengths of about 400 G and no significant electric currents. The sunspot does not fragment, and the LB remains stable for several days. The chromospheric temperature, IRIS line intensities and widths, and AIA 171 and 211 Å intensities are all enhanced in the LB with temperatures from 8000 K to 2.5 MK. Photospheric plasma motions remain small, while the chromosphere and transition region indicate predominantly redshifts of 5–20 km s ^−1 with occasional supersonic downflows exceeding 100 km s ^−1 . The excess thermal energy over the LB is about 3.2 × 10 ^26 erg and matches the radiative losses. It could be supplied by magnetic flux loss of the sunspot (7.5 × 10 ^27 erg), kinetic energy from the increase in the LB width (4 × 10 ^28 erg), or freefall of mass along the coronal loops (6.3 × 10 ^26 erg). |
| first_indexed | 2024-03-12T04:33:48Z |
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| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T04:33:48Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj.art-6361931d07534f3c9a22a445eba94fe22023-09-03T09:58:12ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0194226210.3847/1538-4357/aca612Sustained Heating of the Chromosphere and Transition Region Over a Sunspot Light BridgeRohan E. Louis0https://orcid.org/0000-0001-5963-8293Shibu K. Mathew1https://orcid.org/0000-0002-9370-2591A. Raja Bayanna2https://orcid.org/0000-0001-5802-7677Christian Beck3https://orcid.org/0000-0001-7706-4158Debi P. Choudhary4https://orcid.org/0000-0002-9308-3639Udaipur Solar Observatory , Physical Research Laboratory Dewali Badi Road, Udaipur—313001, Rajasthan, India ; rlouis@prl.res.inUdaipur Solar Observatory , Physical Research Laboratory Dewali Badi Road, Udaipur—313001, Rajasthan, India ; rlouis@prl.res.inUdaipur Solar Observatory , Physical Research Laboratory Dewali Badi Road, Udaipur—313001, Rajasthan, India ; rlouis@prl.res.inNational Solar Observatory (NSO ), 3665 Discovery Drive, Boulder, CO 80303, USADepartment of Physics and Astronomy, California State University , Northridge (CSUN), CA 91330-8268, USASunspot light bridges (LBs) exhibit a wide range of short-lived phenomena in the chromosphere and transition region. In contrast, we use here data from the Multi-Application Solar Telescope (MAST), the Interface Region Imaging Spectrograph (IRIS), Hinode, the Atmospheric Imaging Assembly (AIA), and the Helioseismic and Magnetic Imager (HMI) to analyze the sustained heating over days in an LB in a regular sunspot. Chromospheric temperatures were retrieved from the MAST Ca ii and IRIS Mg ii lines by nonlocal thermodynamic equilibrium inversions. Line widths, Doppler shifts, and intensities were derived from the IRIS lines using Gaussian fits. Coronal temperatures were estimated through the differential emission measure, while the coronal magnetic field was obtained from an extrapolation of the HMI vector field. At the photosphere, the LB exhibits a granular morphology with field strengths of about 400 G and no significant electric currents. The sunspot does not fragment, and the LB remains stable for several days. The chromospheric temperature, IRIS line intensities and widths, and AIA 171 and 211 Å intensities are all enhanced in the LB with temperatures from 8000 K to 2.5 MK. Photospheric plasma motions remain small, while the chromosphere and transition region indicate predominantly redshifts of 5–20 km s ^−1 with occasional supersonic downflows exceeding 100 km s ^−1 . The excess thermal energy over the LB is about 3.2 × 10 ^26 erg and matches the radiative losses. It could be supplied by magnetic flux loss of the sunspot (7.5 × 10 ^27 erg), kinetic energy from the increase in the LB width (4 × 10 ^28 erg), or freefall of mass along the coronal loops (6.3 × 10 ^26 erg).https://doi.org/10.3847/1538-4357/aca612SunspotsSolar magnetic fieldsSolar photosphereSolar chromosphereSolar corona |
| spellingShingle | Rohan E. Louis Shibu K. Mathew A. Raja Bayanna Christian Beck Debi P. Choudhary Sustained Heating of the Chromosphere and Transition Region Over a Sunspot Light Bridge The Astrophysical Journal Sunspots Solar magnetic fields Solar photosphere Solar chromosphere Solar corona |
| title | Sustained Heating of the Chromosphere and Transition Region Over a Sunspot Light Bridge |
| title_full | Sustained Heating of the Chromosphere and Transition Region Over a Sunspot Light Bridge |
| title_fullStr | Sustained Heating of the Chromosphere and Transition Region Over a Sunspot Light Bridge |
| title_full_unstemmed | Sustained Heating of the Chromosphere and Transition Region Over a Sunspot Light Bridge |
| title_short | Sustained Heating of the Chromosphere and Transition Region Over a Sunspot Light Bridge |
| title_sort | sustained heating of the chromosphere and transition region over a sunspot light bridge |
| topic | Sunspots Solar magnetic fields Solar photosphere Solar chromosphere Solar corona |
| url | https://doi.org/10.3847/1538-4357/aca612 |
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