Nonlinear dynamo models using quasi-biennial oscillations constrained by sunspot area data

Abstract

Contex: Solar magnetic activity exhibits variations with periods between 1.5--4 years, the so-called quasi-biennial oscillations (QBOs), in addition to the well-known 11-year Schwabe cycles. Solar dynamo is thought to be the responsible mechanism for generation of the QBOs. Aims: In this work, we analyse sunspot areas to investigate the spatial and temporal behaviour of the QBO signal and study the responsible physical mechanisms using simulations from fully nonlinear mean-field flux-transport dynamos. Methods: We investigated the behaviour of the QBOs in the sunspot area data in full disk, and northern and southern hemispheres, using wavelet and Fourier analyses. We also ran solar dynamos with two different approaches to generating a poloidal field from an existing toroidal field, Babcock-Leighton and turbulent $\alpha$ mechanisms. We then studied the simulated magnetic field strengths as well as meridional circulation and differential rotation rates using the same methods. Results: The results from the sunspot areas show that the QBOs are present in the full disk and hemispheric sunspot areas and they show slightly different spatial and temporal behaviours, indicating a slightly decoupled solar hemispheres. The QBO signal is generally intermittent and in-phase with the sunspot area data, surfacing when the solar activity is in maximum. The results from the BL-dynamos showed that they are neither capable of generating the slightly decoupled behaviour of solar hemispheres nor can they generate QBO-like signals. The turbulent $\alpha$-dynamos, on the other hand, generated decoupled hemispheres and some QBO-like shorter cycles. Conclusions: In conclusion, our simulations show that the turbulent $\alpha$-dynamos with the Lorentz force seems more efficient in generating the observed temporal and spatial behaviour of the QBO signal compared with those from the BL-dynamos.

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Cited by in corpus (12)

• Solar-Cycle Characteristics in Kodaikanal Sunspot Area: North--South Asymmetry, Phase Distribution and Gnevyshev Gap
• The spatial distribution of quasi-biennial oscillations in the high-latitude solar activity
• Spectral characteristic of mid-term quasi-periodicities in sunspots data
• Temporal and Periodic Variation of the MCMESI for the Last Two Solar Cycles; Comparison with the Number of Different Class X-Ray Solar Flares
• Cycle dependency of a quasi-biennial variability in the solar interior
• Temporal evolutions and quasi-periodic variations present in the sunspot number and group sunspot area data measured at Kodaikanal Observatory for solar cycles 14 to 24
• The QBO-type signals in the subsurface flow fields during solar cycles 23 and 24
• Does the mean-field alpha effect have any impact on the memory of the solar cycle?
• Causal Interaction between the subsurface rotation rate residuals and radial magnetic field in different timescales
• First Doppler image and starspot-corrected orbit for $\lambda$ Andromedae: A multifaceted activity analysis
• Nearly Century-scale Variation of the Sun's Radius
• Analysis of Short-term Solar Activity Variability and Estimating the Timings of the Next Enhanced Bursts