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Active regions from split toroidal rings

Presentation #112.05 in the session Understanding Solar Eruptions Using Data-driven Models and Multi-height Observations of the Solar Atmosphere II — Poster Session.

Published onOct 20, 2022
Active regions from split toroidal rings

We simulate the dynamical evolution of narrow spot-producing toroidal rings of 6-degree latitudinal width and peak field of 15 kG at the base of the convection zone. We find that the rings split within a few weeks, due to nonlinear interaction with Rossby waves there, which work as perturbations to drive instability of spot-producing toroidal rings. The ring-split is caused by the ‘mixed stress’, which arises due to cross correlations of perturbation velocities and magnetic fields. By the action of this stress magnetic energy is extracted from the ring-peak and is deposited to its shoulders, eventually leading to the ring-split. The two split-rings migrate away from each other, the high latitude counterpart slipping poleward faster, due to migrating mixed stress and magnetic curvature stress. Broader toroidal bands do not split. Much stronger rings, despite being narrow, don’t split, due to rigidity from stronger magnetic fields within the ring. From analysis of magnetograms and butterfly diagrams, we find that active regions sometimes appear at the same longitudes but separated in latitude by 20-degrees or more, which could be evidence of active regions emerging from split-rings; these active regions consistently contribute to observed high latitude excursions of butterfly wings, such as that observed during Bastille day solar storms. How often new spots are found at higher latitudes than their lower latitude counterparts, and how the combinations influence solar eruptions and space weather events are extensively being explored.

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