Toroidal Flux Loss due to Flux Emergence Explains why Solar Cycles Rise Differently but Decay in a Similar Way

Biswas, Akash; Karak, Bidya Binay; Cameron, R. H.

doi:10.1103/physrevlett.129.241102

Cited by 12 publications

(10 citation statements)

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“…Recently, the Babcock-Leighton mechanism (Babcock 1961;Leighton 1969), in which the tilted bipolar magnetic regions produce poloidal field in the sun, has received strong observational supports (Dasi-Espuig et al 2010;Kitchatinov & Olemskoy 2011;Priyal et al 2014;Cameron & Schüssler 2015). Including this process for the generation of the poloidal field, the Babcock-Leighton type dynamo models have produced great successes in providing many observational features of the solar magnetic cycle, including the grand minima (e.g., Choudhuri & Karak 2012;Karak & Miesch 2017;Cameron & Schüssler 2017;Lemerle & Charbonneau 2017;Inceoglu et al 2017;Biswas et al 2022).…”

mentioning

confidence: 99%

Dynamo modelling for cycle variability and occurrence of grand minima in Sun-like stars: rotation rate dependence

Vashishth

Karak

Kitchatinov

2023

Monthly Notices of the Royal Astronomical Society

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Like the solar cycle, stellar activity cycles are also irregular. Observations reveal that rapidly rotating (young) Sun-like stars exhibit a high level of activity with no Maunder-like grand minima and rarely display smooth regular activity cycles. On the other hand, slowly rotating old stars like the Sun have low activity levels and smooth cycles with occasional grand minima. We, for the first time, try to model these observational trends using flux transport dynamo models. Following previous works, we build kinematic dynamo models of one solar mass star with different rotation rates. Differential rotation and meridional circulation are specified with a mean-field hydrodynamic model. We include stochastic fluctuations in the Babcock–Leighton source of the poloidal field to capture the inherent fluctuations in the stellar convection. Based on extensive simulations, we find that rapidly rotating stars produce highly irregular cycles with strong magnetic fields and rarely produce Maunder-like grand minima, whereas the slowly rotating stars (with a rotation period of 10 d and longer) produce smooth cycles of weaker strength, long-term modulation in the amplitude, and occasional extended grand minima. The average duration and the frequency of grand minima increase with decreasing rotation rate. These results can be understood as the tendency of less supercritical dynamo in slower rotating stars to be more prone to produce extended grand minima.

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confidence: 99%

Dynamo modelling for cycle variability and occurrence of grand minima in Sun-like stars: rotation rate dependence

Vashishth

Karak

Kitchatinov

2023

Monthly Notices of the Royal Astronomical Society

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“…Long-term modulations, including Gnevyshev-Ohl/Odd-Even rule (Charbonneau, 2001;Charbonneau et al, 2007) and grand minima (Charbonneau et al, 2004;Choudhuri and Karak, 2009;Passos et al, 2012 are naturally produced in these models. Variations within the cycle, like the amplitude-period anti-correlation (Charbonneau and Dikpati, 2000;Karak, 2010) and Waldmeier effect (Karak and Choudhuri, 2011;Biswas et al, 2022) are also reproduced. showed that a large variation in the Babcock-Leighton process can change the polar field abruptly and this can lead to double peaks in the following cycle.…”

Section: Babcock-leighton Dynamo Models For the Long-term Variationmentioning

confidence: 81%

“…In an extreme case, a largely reduced meridional circulation can trigger a Maunder-like grand Fig. 7 The trajectories of (a) annual sunspot number and (b) FWHM vs the central latitude of the annual spot distribution obtained from a dynamo simulation with buoyancy-induced flux loss (Biswas et al, 2022). Curves clearly show that the beginning phases of the cycles differ widely depending on their strengths but they decline in the same way irrespective of their strengths.…”

Section: Nonlinearities In the Dynamomentioning

confidence: 99%

“…The sharp rise in the flux loss once the toroidal field strength exceeds a certain value clearly indicates a nonlinear mechanism in the solar dynamo. Incorporating this mechanism of toroidal flux loss due to buoyancy in a simple manner, Biswas et al (2022) showed that this nonlinear process plays a critical role in limiting the growth of the solar dynamo which is a potential mechanism to explain why different solar cycles rise differently depending on their strength but all the solar cycles decay with similar statistical properties (see Figure 7). They found that introducing the flux loss in the dynamo simulations was critical to reproduce the long-term features of the latitudinal distribution of the sunspots (Waldmeier, 1955;Cameron and Schüssler, 2016); also see Cameron and Schüssler (2016) and Talafha et al (2022) for an alternative explanation of the universal decay of the solar cycle using cross-equatorial diffusion.…”

Section: • Flux Loss Due To Magnetic Buoyancymentioning

confidence: 99%

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Long-term modulation of solar cycles

Biswas¹,

Karak²,

Usoskin³

et al. 2023

Preprint

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Solar activity has a cyclic nature with the ≈11-year Schwabe cycle dominating its variability on the interannual timescale. However, solar cycles are significantly modulated in length, shape and magnitude, from near-spotless grand minima to very active grand maxima. The ≈400year-long direct sunspot-number series is inhomogeneous in quality and too short to study robust parameters of long-term solar variability. The cosmogenic-isotope proxy extends the timescale to twelve millennia and provides crucial observational constraints of the long-term solar dynamo modulation. Here, we present a brief up-to-date overview of the long-term variability of solar activity at centennial -millennial timescales. The occurrence of grand minima and maxima is discussed as well as the existing quasi-periodicities such as centennial Gleissberg, 201-year Suess/de Vries and 2400-year Hallstatt cycles. It is shown that the solar cycles contain an important random component and have no clock-like phase locking implying a lack of long-term memory. A brief yet comprehensive review of the theoretical perspectives to explain the observed features in the framework of the dynamo models is presented, including the nonlinearity and stochastic fluctuations in the dynamo. We keep gaining knowledge of the processes driving solar variability with the new data acquainted and new models developed.

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“…Hence, in every cycle during the generation of the poloidal field, the memory of the polar field is degraded. The toroidal to poloidal component of the solar dynamo also involves some nonlinearities, which at least include the flux loss due to magnetic buoyancy in the formation of BMR (Biswas et al 2022), latitude quenching (Jiang 2020;Karak 2020), and tilt quenching (Jha et al 2020). The nonlinearity plays an important role in determining the memory of the polar field when the dynamo becomes supercritical.…”

Section: Introductionmentioning

confidence: 99%

Characterizing the Solar Cycle Variability Using Nonlinear Time Series Analysis at Different Amounts of Dynamo Supercriticality: Solar Dynamo is Not Highly Supercritical

Ghosh,

Kumar,

Prasad

et al. 2024

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The solar dynamo is essentially a cyclic process in which the toroidal component of the magnetic field is converted into the poloidal one and vice versa. This cyclic loop is disturbed by some nonlinear and stochastic processes mainly operating in the toroidal to poloidal part. Hence, the memory of the polar field decreases in every cycle. On the other hand, the dynamo efficiency and, thus, the supercriticality of the dynamo decreases with the Sun’s age. Previous studies have shown that the memory of the polar magnetic field decreases with the increase of supercriticality of the dynamo. In this study, we employ popular techniques of time series analysis, namely, compute Higuchi’s fractal dimension, Hurst exponent, and Multi-Fractal Detrended Fluctuation Analysis to the amplitude of the solar magnetic cycle obtained from dynamo models operating at near-critical and supercritical regimes. We show that the magnetic field in the near-critical regime is governed by strong memory, less stochasticity, intermittency, and breakdown of self-similarity. On the contrary, the magnetic field in the supercritical region has less memory, strong stochasticity, and shows a good amount of self-similarity. Finally, applying the same time series analysis techniques in the reconstructed sunspot data of 85 cycles and comparing their results with that from models, we conclude that the solar dynamo is possibly operating near the critical regime and not too much supercritical regime. Thus the Sun may not be too far from the critical dynamo transition.

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Toroidal Flux Loss due to Flux Emergence Explains why Solar Cycles Rise Differently but Decay in a Similar Way

Cited by 12 publications

References 35 publications

Dynamo modelling for cycle variability and occurrence of grand minima in Sun-like stars: rotation rate dependence

Dynamo modelling for cycle variability and occurrence of grand minima in Sun-like stars: rotation rate dependence

Long-term modulation of solar cycles

Characterizing the Solar Cycle Variability Using Nonlinear Time Series Analysis at Different Amounts of Dynamo Supercriticality: Solar Dynamo is Not Highly Supercritical

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