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Eruptions from quiet Sun coronal bright points : II. Non-potential modelling

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Galsgaard_2019_Eruption_from_quiet_Sun_A_A_A78.pdf (3.583Mb)
Date
03/2019
Author
Galsgaard, Klaus
Madjarska, Maria
Mackay, Duncan H.
Mou, Chaozhou
Keywords
Methods: observational, numerical
Sun: eruptions, magnetic fields
Techniques: NLFFF relaxation
QB Astronomy
QC Physics
3rd-DAS
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Abstract
Context. Our recent observational study shows that the majority of coronal bright points (CBPs) in the quiet Sun are sources of one or more eruptions during their lifetime. Aims. Here, we investigate the non-potential time-dependent structure of the magnetic field of the CBP regions with special emphasison the time-evolving magnetic structure at the spatial locations where the eruptions are initiated. Methods. The magnetic structure is evolved in time using a non-linear force-free field (NLFFF) relaxation approach based on a timeseries of helioseismic and magnetic imager (HMI) longitudinal magnetograms. This results in a continuous time series of NLFFFs.The time series is initiated with a potential field extrapolation based on a magnetogram taken well before the time of the eruptions. This initial field is then evolved in time in response to the observed changes in the magnetic field distribution at the photosphere. The local and global magnetic field structures from the time series of NLFFF field solutions are analysed in the vicinity of the eruption sites at the approximate times of the eruptions. Results. The analysis shows that many of the CBP eruptions reported in a recent publication contain twisted flux tube located atthe sites of eruptions. The presence of flux ropes at these locations provides in many cases a direct link between the magnetic field structure, their eruption, and the observation of mini coronal mass ejections (mini-CMEs). It is found that all repetitive eruptions are homologous. Conclusions. The NLFFF simulations show that twisted magnetic field structures are created at the locations hosting eruptions inCBPs. These twisted structures are produced by footpoint motions imposed by changes in the photospheric magnetic field observations.The true nature of the micro-flares remains unknown. Further 3D data-driven magnetohydrodynamic modelling is required to show how these twisted regions become unstable and erupt.
Citation
Galsgaard , K , Madjarska , M , Mackay , D H & Mou , C 2019 , ' Eruptions from quiet Sun coronal bright points : II. Non-potential modelling ' , Astronomy & Astrophysics , vol. 623 , A78 . https://doi.org/10.1051/0004-6361/201834329
Publication
Astronomy & Astrophysics
Status
Peer reviewed
DOI
https://doi.org/10.1051/0004-6361/201834329
ISSN
0004-6361
Type
Journal article
Rights
© 2019, ESO. This work has been made available online in accordance with the publisher's policies. This is the final published version of the work, which was originally published at https://doi.org/10.1051/0004-6361/201834329
Description
Support for VAPOR is provided by the U.S. National Science Foundation (grants # 03-25934 and 09-06379, ACI-14-40412), and by the Korea Institute of Science and Technology Information. C. M. thanks the National Natural Science Foundation of China (41474150). The HMI data are provided courtesy of NASA/SDO and corresponding science teams. The HMI data have been retrieved using the Stanford University’s Joint Science Operations Centre/Science Data Processing Facility. M.M. and K.G. thank the ISSI Bern for the support to the team “Observation-Driven Modelling of Solar Phenomena”.
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  • University of St Andrews Research
URI
http://hdl.handle.net/10023/17015

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