Stellar mid-life crisis: subcritical magnetic dynamos of solar-like stars and the breakdown of gyrochronology
In: Monthly Notices of the Royal Astronomical Society: Letters, Jg. 506 (2021-07-28), S. L50- (5S.)
Online
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Zugriff:
Recent observations reveal the surprising breakdown of stellar gyrochronology relations at about the Sun's age hinting that middle-aged, solar-like stars transition to a magnetically inactive future. We provide a theoretical basis for these intriguing observations inspired by simulations with a mathematical dynamo model that can explore long-term solar cycle fluctuations. We reproduce the observed bimodal distribution of sunspot numbers, but only for subcritical dynamos. Based on a bifurcation analysis, we argue that ageing of solar-like stars makes the magnetically-weak dynamo regime readily accessible. Weak magnetic field production in this regime compromises wind-driven angular momentum losses thus disrupting the hegemony of magnetic braking on stellar rotational spin-down. This hypothesis of {\emph{subcritical magnetic dynamos}} of solar-like stars provides a self-consistent, unifying physical basis for a diversity of solar-stellar phenomena such as why stars beyond their mid-life do not spin-down as fast as in their youth, the break-down of stellar gyrochronology relations, the observed bimodal distribution of long-term sunspot observations and recent findings suggesting that the Sun may be transitioning to a magnetically inactive future.
Comment: Press release by the Royal Astronomical Society, UK, at https://ras.ac.uk/news-and-press/research-highlights/magnetic-fields-implicated-mysterious-midlife-crisis-stars
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Stellar mid-life crisis: subcritical magnetic dynamos of solar-like stars and the breakdown of gyrochronology
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Autor/in / Beteiligte Person: | Nandy, Dibyendu ; Tripathi, Bindesh ; Banerjee, Soumitro |
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Zeitschrift: | Monthly Notices of the Royal Astronomical Society: Letters, Jg. 506 (2021-07-28), S. L50- (5S.) |
Veröffentlichung: | Oxford University Press (OUP), 2021 |
Medientyp: | unknown |
ISSN: | 1745-3933 (print) ; 1745-3925 (print) |
DOI: | 10.1093/mnrasl/slab035 |
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