- Title
- A flux-independent increase in outflows prior to the emergence of active regions on the Sun
- Creator
- Schunker, H.; Roland-Batty, W.; Birch, A. C.; Braun, D. C.; Cameron, R. H.; Gizon, L.
- Relation
- ARC.FT220100330
- Relation
- Monthly Notices of the Royal Astronomical Society Vol. 533, Issue 1, p. 225-243
- Publisher Link
- http://dx.doi.org/10.1093/mnras/stae1776
- Publisher
- Oxford University Press
- Resource Type
- journal article
- Date
- 2024
- Description
- Emerging active regions are associated with convective flows on the spatial scale and lifetimes of supergranules. To understand how these flows are involved in the formation of active regions, we aim to identify where active regions emerge in the supergranulation flow pattern. We computed supergranulation scale flow maps at the surface for all active regions in the Solar Dynamics Observatory Helioseismic Emerging Active Region Survey. We classified each of the active regions into four bins based on the amplitude of their average surface flow divergence at emergence. We then averaged the flow divergence over the active regions in each bin as a function of time. We also considered a corresponding set of control regions. We found that, on average, the flow divergence increases during the day prior to emergence at a rate independent of the amount of flux that emerges. By subtracting the averaged flow divergence of the control regions, we found that active region emergence is associated with a remaining converging flow at 0.5-1 d prior to emergence. This remnant flow, corresponds to a flow speed of 10-20 m s-1 (an order of magnitude less than supergranulation flows) out to a radius of about 10 Mm. We show that these observational results are qualitatively supported by simulations of a small bipole emerging through the near-surface convective layers of the Sun. The question remains whether these flows are driving the emergence, or are caused by the emergence.
- Subject
- Sun: magnetic fields; helioseismology; activity; active regions
- Identifier
- http://hdl.handle.net/1959.13/1512141
- Identifier
- uon:56589
- Identifier
- ISSN:0035-8711
- Rights
- © 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
- Language
- eng
- Full Text
- Reviewed
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