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Deciphering the Pre–solar-storm Features of the 2017 September Storm From Global and Local Dynamics

Raphaldini, Breno; Dikpati, Mausumi; Norton, Aimee A.; Teruya, Andre S. W.; McIntosh, Scott W.; Prior, Christopher B.; MacTaggart, David

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Breno Raphaldini

Mausumi Dikpati

Aimee A. Norton

Andre S. W. Teruya

Scott W. McIntosh

David MacTaggart


We investigate whether global toroid patterns and the local magnetic field topology of solar active region (AR) 12673 together can hindcast the occurrence of the biggest X-flares of solar cycle (SC)-24. Magnetic toroid patterns (narrow latitude belts warped in longitude, in which ARs are tightly bound) derived from the surface distributions of ARs, prior and during AR 12673 emergence, reveal that the portions of the south toroid containing AR 12673 was not tipped away from its north-toroid counterpart at that longitude, unlike the 2003 Halloween storms scenario. During the minimum phase there were too few emergences to determine multimode longitudinal toroid patterns. A new emergence within AR 12673 produced a complex nonpotential structure, which led to the rapid buildup of helicity and winding that triggered the biggest X-flare of SC-24, suggesting that this minimum-phase storm can be anticipated several hours before its occurrence. However, global patterns and local dynamics for a peak-phase storm, such as that from AR 11263, behaved like the 2003 Halloween storms, producing the third biggest X-flare of SC-24. AR 11263 was present at the longitude where the north and south toroids tipped away from each other. While global toroid patterns indicate that prestorm features can be forecast with a lead time of a few months, their application to observational data can be complicated by complex interactions with turbulent flows. Complex nonpotential field structure development hours before the storm are necessary for short-term prediction. We infer that minimum-phase storms cannot be forecast accurately more than a few hours ahead, while flare-prone ARs in the peak phase may be anticipated much earlier, possibly months ahead from global toroid patterns.


Raphaldini, B., Dikpati, M., Norton, A. A., Teruya, A. S. W., McIntosh, S. W., Prior, C. B., & MacTaggart, D. (2023). Deciphering the Pre–solar-storm Features of the 2017 September Storm From Global and Local Dynamics. Astrophysical Journal, 958(2), Article 175.

Journal Article Type Article
Acceptance Date Sep 26, 2023
Online Publication Date Nov 23, 2023
Publication Date Dec 1, 2023
Deposit Date Nov 29, 2023
Publicly Available Date Nov 29, 2023
Journal The Astrophysical Journal
Print ISSN 0004-637X
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 958
Issue 2
Article Number 175
Keywords Solar ARs, Solar activity, Solar storm, Solar flares
Public URL


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