Wang, D., Liu, R. orcid.org/0000-0003-4618-4979, Wang, Y. orcid.org/0000-0002-8887-3919 et al. (5 more authors) (2017) Critical Height of the Torus Instability in Two-ribbon Solar Flares. The Astrophysical Journal, 843 (1). L9-L9. ISSN 2041-8205
Abstract
We studied the background field for 60 two-ribbon flares of M-and-above classes during 2011–2015. These flares are categorized into two groups, i.e., eruptive and confined flares, based on whether a flare is associated with a coronal mass ejection or not. The background field of source active regions is approximated by a potential field extrapolated from the Bz component of vector magnetograms provided by the Helioseismic and Magnetic Imager. We calculated the decay index n of the background field above the flaring polarity inversion line, and defined a critical height hcrit corresponding to the theoretical threshold (ncrit = 1.5) of the torus instability. We found that hcrit is approximately half of the distance between the centroids of opposite polarities in active regions and that the distribution of hcrit is bimodal: it is significantly higher for confined flares than for eruptive ones. The decay index increases monotonously with increasing height for 86% (84%) of the eruptive (confined) flares but displays a saddle-like profile for the rest, 14% (16%), which are found exclusively in active regions of multipolar field configuration. Moreover, n at the saddle bottom is significantly smaller in confined flares than that in eruptive ones. These results highlight the critical role of background field in regulating the eruptive behavior of two-ribbon flares
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2017. The American Astronomical Society. Reproduced in accordance with the publisher's self-archiving policy. |
Keywords: | instabilities; Sun: coronal mass ejections (CMEs); Sun: flares; Sun: magnetic fields |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > School of Mathematics and Statistics (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 20 Jul 2017 13:52 |
Last Modified: | 20 Jul 2017 13:52 |
Published Version: | http://doi.org/10.3847/2041-8213/aa79f0 |
Status: | Published |
Publisher: | American Astronomical Society |
Refereed: | Yes |
Identification Number: | 10.3847/2041-8213/aa79f0 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:119128 |