Varying Calcium Abundances in Solar Flares Seen by the Solar Maximum Mission
We report on calcium abundance A (Ca) estimates during the decay phases of 194 solar X-ray flares using archived data from the Bent Crystal Spectrometer (BCS) on the Solar Maximum Mission (operational 1980–1989). The abundances are derived from the ratio of the total calcium X-ray line emission in B...
| 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/acc016 |
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| author | B. Sylwester J. Sylwester K. J. H. Phillips A. Kępa |
| author_facet | B. Sylwester J. Sylwester K. J. H. Phillips A. Kępa |
| author_sort | B. Sylwester |
| collection | DOAJ |
| description | We report on calcium abundance A (Ca) estimates during the decay phases of 194 solar X-ray flares using archived data from the Bent Crystal Spectrometer (BCS) on the Solar Maximum Mission (operational 1980–1989). The abundances are derived from the ratio of the total calcium X-ray line emission in BCS channel 1 to that in neighboring continuum, with temperature from a satellite-to-resonance line ratio. Generally, the calcium abundance is found to be about 3 times the photospheric abundance, as previously found, indicating a “first ionization potential” (FIP) effect for calcium, which has a relatively low FIP value. The precision of the abundance estimates (referred to hydrogen on a logarithmic scale with A (H) = 12), is typically ∼± 0.01, enabling any time variations of A (Ca) during the flare decay to be examined. For a total of 270 short time segments with A (Ca) determined to better than 2.3% accuracy, many (106; 39%) showed variations in A (Ca) at the 3 σ level. For the majority, in 74 (70%) of these 106 segments A (Ca) decreased with time, and for 32 (30%) A (Ca) increased with time. For 79 out of 270 (29%) we observed constant or nearly constant A (Ca), and the remaining 85 (31%) with irregular time behavior. A common feature was the presence of discontinuities in the time behavior of A (Ca). Relating these results to the ponderomotive force theory of Laming, we attribute the nature of varying A (Ca) to the emergence of loop structures in addition to the initial main loop, each with its characteristic calcium abundance. |
| first_indexed | 2024-03-12T03:16:53Z |
| format | Article |
| id | doaj.art-514e37aa760840c8b663113d0a75ea31 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T03:16:53Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-514e37aa760840c8b663113d0a75ea312023-09-03T14:08:23ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0194614910.3847/1538-4357/acc016Varying Calcium Abundances in Solar Flares Seen by the Solar Maximum MissionB. Sylwester0https://orcid.org/0000-0001-8428-4626J. Sylwester1https://orcid.org/0000-0002-8060-0043K. J. H. Phillips2https://orcid.org/0000-0002-3790-990XA. Kępa3https://orcid.org/0000-0002-5299-5404Space Research Centre , Polish Academy of Sciences (CBK PAN), Warsaw, Bartycka 18A, Poland ; bs@cbk.pan.wroc.pl, js@cbk.pan.wroc.pl, ak@cbk.pan.wroc.plSpace Research Centre , Polish Academy of Sciences (CBK PAN), Warsaw, Bartycka 18A, Poland ; bs@cbk.pan.wroc.pl, js@cbk.pan.wroc.pl, ak@cbk.pan.wroc.plScientific Associate, Earth Sciences Department, Natural History Museum , Cromwell Road, London, SW7 5BD, UK ; kennethjhphillips@yahoo.comSpace Research Centre , Polish Academy of Sciences (CBK PAN), Warsaw, Bartycka 18A, Poland ; bs@cbk.pan.wroc.pl, js@cbk.pan.wroc.pl, ak@cbk.pan.wroc.plWe report on calcium abundance A (Ca) estimates during the decay phases of 194 solar X-ray flares using archived data from the Bent Crystal Spectrometer (BCS) on the Solar Maximum Mission (operational 1980–1989). The abundances are derived from the ratio of the total calcium X-ray line emission in BCS channel 1 to that in neighboring continuum, with temperature from a satellite-to-resonance line ratio. Generally, the calcium abundance is found to be about 3 times the photospheric abundance, as previously found, indicating a “first ionization potential” (FIP) effect for calcium, which has a relatively low FIP value. The precision of the abundance estimates (referred to hydrogen on a logarithmic scale with A (H) = 12), is typically ∼± 0.01, enabling any time variations of A (Ca) during the flare decay to be examined. For a total of 270 short time segments with A (Ca) determined to better than 2.3% accuracy, many (106; 39%) showed variations in A (Ca) at the 3 σ level. For the majority, in 74 (70%) of these 106 segments A (Ca) decreased with time, and for 32 (30%) A (Ca) increased with time. For 79 out of 270 (29%) we observed constant or nearly constant A (Ca), and the remaining 85 (31%) with irregular time behavior. A common feature was the presence of discontinuities in the time behavior of A (Ca). Relating these results to the ponderomotive force theory of Laming, we attribute the nature of varying A (Ca) to the emergence of loop structures in addition to the initial main loop, each with its characteristic calcium abundance.https://doi.org/10.3847/1538-4357/acc016Solar flares |
| spellingShingle | B. Sylwester J. Sylwester K. J. H. Phillips A. Kępa Varying Calcium Abundances in Solar Flares Seen by the Solar Maximum Mission The Astrophysical Journal Solar flares |
| title | Varying Calcium Abundances in Solar Flares Seen by the Solar Maximum Mission |
| title_full | Varying Calcium Abundances in Solar Flares Seen by the Solar Maximum Mission |
| title_fullStr | Varying Calcium Abundances in Solar Flares Seen by the Solar Maximum Mission |
| title_full_unstemmed | Varying Calcium Abundances in Solar Flares Seen by the Solar Maximum Mission |
| title_short | Varying Calcium Abundances in Solar Flares Seen by the Solar Maximum Mission |
| title_sort | varying calcium abundances in solar flares seen by the solar maximum mission |
| topic | Solar flares |
| url | https://doi.org/10.3847/1538-4357/acc016 |
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