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dc.contributor.author
Ryan, Daniel F.
dc.contributor.author
Laube, S.
dc.contributor.author
Nicula, B.
dc.contributor.author
Krucker, S.
dc.contributor.author
Maloney, S.A.
dc.contributor.author
Battaglia, A.F.
dc.contributor.author
Warmuth, A.
dc.contributor.author
Csillaghy, A.
dc.contributor.author
Müller, D.
dc.date.accessioned
2024-02-05T12:25:58Z
dc.date.available
2024-01-30T09:15:38Z
dc.date.available
2024-02-05T12:25:58Z
dc.date.issued
2024-01
dc.identifier.issn
0004-6361
dc.identifier.issn
1432-0746
dc.identifier.other
10.1051/0004-6361/202347212
en_US
dc.identifier.uri
http://hdl.handle.net/20.500.11850/656436
dc.identifier.doi
10.3929/ethz-b-000656436
dc.description.abstract
Context. The recent launch of Solar Orbiter has placed a solar X-ray imager (Spectrometer/Telescope for Imaging X-rays; STIX) beyond Earth orbit for the first time. This introduces the possibility of deriving the 3D locations and volumes of solar X-ray sources by combining STIX observations with those of Earth-orbiting instruments such as the Hinode X-ray Telescope (XRT). These measurements promise to improve our understanding of the evolution and energetics of solar flares. However, substantial design differences between STIX and XRT present important challenges that must first be overcome.Aims. We aim to: 1) explore the validity of combining STIX and XRT for 3D analysis given their different designs, 2) understand uncertainties associated with 3D reconstruction and their impact on the derived volume and thermodynamic properties, 3) determine the validity of the scaling law that is traditionally used to estimate source volumes from single-viewpoint observations, 4) chart the temporal evolution of the location, volume, and thermodynamic properties of a thermal X-ray loop-top source of a flare based on a 3D reconstruction for the first time.Methods. The SOL2021-05-07T18:43 M3.9-class flare is analysed using co-temporal observations from STIX and XRT, which, at the time, were separated by an angle of 95.4 degrees relative to the flare site. The 3D reconstruction is performed via elliptical tie-pointing and the visualisation by JHelioviewer, which is enabled by new features developed for this project. Uncertainties associated with the 3D reconstruction are derived from an examination of projection effects given the observer separation angle and the source orientation and elongation.Results. Firstly, we show that it is valid to combine STIX 6-10 keV and XRT Be-thick observations for 3D analysis for the flare examined in this study. However, the validity of doing so in other cases may depend on the nature of the observed source. Therefore, careful consideration should be given on a case-by-case basis. Secondly, the optimal observer separation angle for 3D reconstruction is 90 degrees +/- 5 degrees, but the uncertainties are still relatively small in the range 90 degrees +/- 20 degrees. Other angles are viable, but are associated with higher uncertainties, which can be quantified. Thirdly, the traditional area-to-volume scaling law may overestimate the 3D-derived volume of the thermal X-ray loop-top source studied here by over a factor of 2. This is beyond the uncertainty of the 3D reconstruction. The X-ray source was not very asymmetric, and so the overestimation may be greater for more elongated sources. In addition, the degree of overestimation can vary with time and viewing angle, demonstrating that the true source geometry can evolve differently in different dimensions. 3D reconstruction is therefore necessary to derive more reliable volumes. Simply applying a modified scaling law to single-viewpoint observations is not sufficient. Finally, the vertical motion of the X-ray source is consistent with previous observations of limb flares. This indicates that 3D reconstruction by elliptical tie-pointing provides reliable 3D locations. The uncertainties of thermodynamic properties derived from volume, temperature, and/or emission measure are dominated by those of the volume. In contrast to single-viewpoint studies, observationally constrained volume uncertainties can be assigned via 3D reconstruction, which lends quantifiable credibility to scientific conclusions drawn from the derived thermodynamic properties.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
EDP Sciences
en_US
dc.rights.uri
http://creativecommons.org/licenses/by/4.0/
dc.subject
Sun: X-rays
en_US
dc.subject
gamma rays
en_US
dc.subject
Sun: flares
en_US
dc.subject
methods: data analysis
en_US
dc.subject
methods: observational
en_US
dc.subject
techniques: image processing
en_US
dc.title
3D evolution of a solar flare thermal X-ray loop-top source
en_US
dc.type
Journal Article
dc.rights.license
Creative Commons Attribution 4.0 International
dc.date.published
2024-01-11
ethz.journal.title
Astronomy & Astrophysics
ethz.journal.volume
681
en_US
ethz.journal.abbreviated
Astron. Astrophys.
ethz.pages.start
A61
en_US
ethz.size
17 p.
en_US
ethz.version.deposit
publishedVersion
en_US
ethz.identifier.wos
ethz.identifier.scopus
ethz.publication.status
published
en_US
ethz.date.deposited
2024-01-30T09:15:46Z
ethz.source
WOS
ethz.eth
yes
en_US
ethz.availability
Open access
en_US
ethz.rosetta.installDate
2024-02-05T12:25:59Z
ethz.rosetta.lastUpdated
2024-02-05T12:25:59Z
ethz.rosetta.exportRequired
true
ethz.rosetta.versionExported
true
ethz.COinS
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