Observational evidence of spot-producing magnetic ring's split during MHD evolution
Abstract
Spot-producing toroidal rings of 6-degree latitudinal width, with peak field of 15 kG, have been found to undergo dynamical splitting due to nonlinear MHD. Split-time depends on the latitude-location of the ring. Ring-splitting occurs fastest, within a few weeks, at latitudes 20-25 degrees. Rossby waves work as perturbations to drive instability of spot-producing toroidal rings. The ring-split is caused by the `mixed stress' or cross correlations of perturbation velocities and magnetic fields, which arise due to the interaction of Rossby Waves. Mixed stress carries magnetic energy and flux from the ring-peak 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 of 35 kG, despite being narrow, don't split, due to rigidity from stronger magnetic fields within the ring. The analysis of magnetograms from MDI during solar cycle 23 indicates emergence of active regions sometimes at the same longitudes but separated in latitude by 20-degrees or more, which could be evidence of active regions emerging from split-rings, which consistently contribute to occasional high latitude excursions of observed butterfly wings during ascending, peak and descending phases of a solar cycle. In the future, observational studies using much longer term magnetograms including GONG and SDO/HMI can determine 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.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMSH55D1876N