First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP: The Anatomy of an Umbral Flash
The Visible Spectro-Polarimeter of the NSF Daniel K. Inouye Solar Telescope collected its Science Verification data on 2021 May 7–8. The instrument observed multiple layers of a sunspot atmosphere simultaneously, in passbands of Ca ii 397 nm (H line), Fe i 630 nm, and Ca ii 854 nm, scanning the regi...
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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 Letters |
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| Online Access: | https://doi.org/10.3847/2041-8213/acb8b5 |
| _version_ | 1827831328600489984 |
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| author | Ryan J. French Thomas J. Bogdan Roberto Casini Alfred G. de Wijn Philip G. Judge |
| author_facet | Ryan J. French Thomas J. Bogdan Roberto Casini Alfred G. de Wijn Philip G. Judge |
| author_sort | Ryan J. French |
| collection | DOAJ |
| description | The Visible Spectro-Polarimeter of the NSF Daniel K. Inouye Solar Telescope collected its Science Verification data on 2021 May 7–8. The instrument observed multiple layers of a sunspot atmosphere simultaneously, in passbands of Ca ii 397 nm (H line), Fe i 630 nm, and Ca ii 854 nm, scanning the region with a spatial sampling of 0.″041 and an average temporal cadence of 7.76 s, for a duration of 38.8 minutes. The slit moved southward across the plane of sky at 3.83 km s ^−1 . The spectropolarimetric scans exhibit prominent oscillatory “ridge” structures that lie nearly perpendicular to the direction of slit motion (north to south). These ridges are visible in the maps of line intensity, central wavelength, line width, and both linear and circular polarization. Contemporaneous Atmospheric Imaging Assembly observations indicate that these ridges are purely temporal in character and are likely attributed to the familiar chromospheric 3 minute umbral oscillations. We observe in detail a steady umbral flash near the center of the sunspot umbra. Although bad seeing limited the spatial resolution, the unique high signal-to-noise ratio data enable us to estimate the shock Mach numbers (≈2), propagation speeds (≈9 km s ^−1 ), and their impacts on the longitudinal magnetic field (Δ B ≈ 50 G), gas pressure, and temperature (Δ T / T ≈ 0.1) of subshocks over 30 s. We also find evidence for rarefaction waves situated between neighboring wave train shocks. The Ca ii 854 nm line width is fairly steady throughout the umbral flash, except for a sharp 1.5 km s ^−1 dip immediately before, and a comparable spike immediately after, the passage of the shock front. This zigzag in line width is centered on the subshock and extends over 0.″4. |
| first_indexed | 2024-03-12T04:43:02Z |
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| issn | 2041-8205 |
| language | English |
| last_indexed | 2024-03-12T04:43:02Z |
| publishDate | 2023-01-01 |
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| series | The Astrophysical Journal Letters |
| spelling | doaj.art-832fe981400f42bcac34bcb0a07f28b62023-09-03T09:30:40ZengIOP PublishingThe Astrophysical Journal Letters2041-82052023-01-019452L2710.3847/2041-8213/acb8b5First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP: The Anatomy of an Umbral FlashRyan J. French0https://orcid.org/0000-0001-9726-0738Thomas J. Bogdan1Roberto Casini2https://orcid.org/0000-0001-6990-513XAlfred G. de Wijn3https://orcid.org/0000-0002-5084-4661Philip G. Judge4https://orcid.org/0000-0001-5174-0568National Solar Observatory , 3665 Innovation Drive, Boulder, CO 80303, USA; Mullard Space Science Laboratory, University College London , Dorking, RH5 6NT, UKNational Solar Observatory , 3665 Innovation Drive, Boulder, CO 80303, USAHAO, National Center for Atmospheric Research , P.O. Box 3000, Boulder, CO 80307-3000, USAHAO, National Center for Atmospheric Research , P.O. Box 3000, Boulder, CO 80307-3000, USAHAO, National Center for Atmospheric Research , P.O. Box 3000, Boulder, CO 80307-3000, USAThe Visible Spectro-Polarimeter of the NSF Daniel K. Inouye Solar Telescope collected its Science Verification data on 2021 May 7–8. The instrument observed multiple layers of a sunspot atmosphere simultaneously, in passbands of Ca ii 397 nm (H line), Fe i 630 nm, and Ca ii 854 nm, scanning the region with a spatial sampling of 0.″041 and an average temporal cadence of 7.76 s, for a duration of 38.8 minutes. The slit moved southward across the plane of sky at 3.83 km s ^−1 . The spectropolarimetric scans exhibit prominent oscillatory “ridge” structures that lie nearly perpendicular to the direction of slit motion (north to south). These ridges are visible in the maps of line intensity, central wavelength, line width, and both linear and circular polarization. Contemporaneous Atmospheric Imaging Assembly observations indicate that these ridges are purely temporal in character and are likely attributed to the familiar chromospheric 3 minute umbral oscillations. We observe in detail a steady umbral flash near the center of the sunspot umbra. Although bad seeing limited the spatial resolution, the unique high signal-to-noise ratio data enable us to estimate the shock Mach numbers (≈2), propagation speeds (≈9 km s ^−1 ), and their impacts on the longitudinal magnetic field (Δ B ≈ 50 G), gas pressure, and temperature (Δ T / T ≈ 0.1) of subshocks over 30 s. We also find evidence for rarefaction waves situated between neighboring wave train shocks. The Ca ii 854 nm line width is fairly steady throughout the umbral flash, except for a sharp 1.5 km s ^−1 dip immediately before, and a comparable spike immediately after, the passage of the shock front. This zigzag in line width is centered on the subshock and extends over 0.″4.https://doi.org/10.3847/2041-8213/acb8b5Active solar chromosphereSolar chromosphereShocksSolar oscillationsSunspotsSolar active region magnetic fields |
| spellingShingle | Ryan J. French Thomas J. Bogdan Roberto Casini Alfred G. de Wijn Philip G. Judge First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP: The Anatomy of an Umbral Flash The Astrophysical Journal Letters Active solar chromosphere Solar chromosphere Shocks Solar oscillations Sunspots Solar active region magnetic fields |
| title | First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP: The Anatomy of an Umbral Flash |
| title_full | First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP: The Anatomy of an Umbral Flash |
| title_fullStr | First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP: The Anatomy of an Umbral Flash |
| title_full_unstemmed | First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP: The Anatomy of an Umbral Flash |
| title_short | First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP: The Anatomy of an Umbral Flash |
| title_sort | first observation of chromospheric waves in a sunspot by dkist visp the anatomy of an umbral flash |
| topic | Active solar chromosphere Solar chromosphere Shocks Solar oscillations Sunspots Solar active region magnetic fields |
| url | https://doi.org/10.3847/2041-8213/acb8b5 |
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