scholarly journals Exploring the Cycle Period and Parity of Stellar Magnetic Activity with Dynamo Modeling

2019 ◽  
Vol 884 (1) ◽  
pp. 35 ◽  
Author(s):  
Gopal Hazra ◽  
Jie Jiang ◽  
Bidya Binay Karak ◽  
Leonid Kitchatinov
1996 ◽  
Vol 176 ◽  
pp. 261-268
Author(s):  
R.A. Donahue

Knowledge of the solar sunspot cycle extends back to the mid-19th century with the work of Schwabe (1843) and Wolf (1856). The mean cycle period of the Sun is 11 years, however, individual cycle lengths range from 7 to 13 years (Eddy 1977). In this century, however, the length of the solar cycle has been closer to 10 years (Donahue and Baliunas 1992a). A complete explanation of the solar magnetic activity and its variations has not yet been produced, although a hydromagnetic dynamo is frequently posited as the source of solar (and therefore stellar) magnetic activity. Empirical measurements of those stars in the H-R Diagram which have convective zones and surface magnetic activity provide the boundary conditions and the range of behavior which must be explained by any all-encompassing theory explaining stellar magnetic activity, and activity cycles.


2006 ◽  
Vol 365 (1) ◽  
pp. 181-190 ◽  
Author(s):  
S. Baliunas ◽  
P. Frick ◽  
D. Moss ◽  
E. Popova ◽  
D. Sokoloff ◽  
...  

1983 ◽  
Vol 102 ◽  
pp. 499-502
Author(s):  
Robert W. Noyes

Recent observational and theoretical findings have clarified the physical mechanisms which underlie magnetic activity production in stars, and point the way naturally to a number of new or more crisply defined questions, whose answers can lead to major progress in the near future. Concerning observational programs, a guiding principle has been evident throughout this symposium: We should rely heavily on the Sun for understanding the detailed physics of magnetic activity and its generation, while at the same time we study analogous stellar phenomena for comparison with the Sun, and for new insights and extension to different regions. I list below some broad observational areas in which conditions seem ripe for important progress in understanding solar and stellar magnetic activity, leaving to other summarizers the discussion of particular observational programs.


1998 ◽  
Vol 498 (1) ◽  
pp. L51-L54 ◽  
Author(s):  
Axel Brandenburg ◽  
Steven H. Saar ◽  
Christen R. Turpin

2020 ◽  
Vol 495 (4) ◽  
pp. 4557-4569 ◽  
Author(s):  
Naveen Jingade ◽  
Nishant K Singh

ABSTRACT We study mean field dynamo action in a background linear shear flow by employing pulsed renewing flows with fixed kinetic helicity and non-zero correlation time (τ). We use plane shearing waves in terms of time-dependent exact solutions to the Navier–Stokes equation as derived by Singh & Sridhar (2017). This allows us to self-consistently include the anisotropic effects of shear on the stochastic flow. We determine the average response tensor governing the evolution of mean magnetic field, and study the properties of its eigenvalues that yield the growth rate (γ) and the cycle period (Pcyc) of the mean magnetic field. Both, γ and the wavenumber corresponding to the fastest growing axisymmetric mode vary non-monotonically with shear rate S when τ is comparable to the eddy turnover time T, in which case, we also find quenching of dynamo when shear becomes too strong. When $\tau /T\sim {\cal O}(1)$, the cycle period (Pcyc) of growing dynamo wave scales with shear as Pcyc ∝ |S|−1 at small shear, and it becomes nearly independent of shear as shear becomes too strong. This asymptotic behaviour at weak and strong shear has implications for magnetic activity cycles of stars in recent observations. Our study thus essentially generalizes the standard αΩ (or α2Ω) dynamo as also the α effect is affected by shear and the modelled random flow has a finite memory.


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