Journal ArticleDOI
Double magnetic cycle of solar activity
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TLDR
In this paper, surface large-scale solar magnetic fields are analyzed using a two-dimensional Fourier method technique to study the poloidal field distribution, and the results obtained confirm the idea that low-frequency dynamo waves with a period approximately equal to 22 years and a high-frequency wave of a quasi-two-year period can coexist.Abstract:
The source of the poloidal magnetic field was fixed using a uniform series of surface low-resolution magnetic field observations begun at Wilcox Solar Observatory at Stanford. The results obtained confirm the idea that low-frequency dynamo waves with a period approximately equal to 22 years and a high-frequency wave of a quasi-two-year period can coexist. It seems that an interaction between these components in the convection zone takes place on the Sun. Surface large-scale solar magnetic fields are analyzed using a two-dimensional Fourier method technique to study the poloidal field distribution. The first harmonic approximately equals the period of the magnetic cycle, appears at all latitudes, and reaches its the maximum value in the polar regions. Moreover, spectral analyses of axisymmetric magnetic field derivative in time found that the second important harmonic of a period approximately equal to two years appears at all latitudes. This second high-frequency harmonic dominates the polar latitude regions at the same time as the low-frequency one.read more
Citations
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Journal ArticleDOI
The Solar Cycle
TL;DR: An examination of prediction techniques for the solar cycle is examined and a closer look at cycles 23 and 24 is taken.
Journal ArticleDOI
Solar Dynamo Theory
TL;DR: A review on solar dynamo theory is structured around three areas in recent years: (a) global magnetohydrodynamical simulations of convection and magnetic cycles, (b) the turbulent electromotive force and the dynamo saturation problem, and (c) flux transport dynamos, and their application to model cycle fluctuations as mentioned in this paper.
Journal ArticleDOI
A Combined Analysis of the Observational Aspects of the Quasi-biennial Oscillation in Solar Magnetic Activity
G. A. Bazilevskaya,Anne-Marie Broomhall,Yvonne Elsworth,Valery M. Nakariakov,Valery M. Nakariakov +4 more
TL;DR: The exact mechanism by which the solar quasi-biennial oscillations (QBOs) are produced is poorly understood as mentioned in this paper, but some of the most plausible theoretical mechanisms and observational features that support/contradict the theory are discussed.
Journal ArticleDOI
Global seismology of the Sun
TL;DR: In this article, the authors discuss some of the techniques used in helioseismic analyses and the results obtained using those techniques and briefly touch upon asteroseismology, the seismic study of stars other than the Sun, and discuss how seismic data of others stars are interpreted.
Journal ArticleDOI
A seismic signature of a second dynamo
Stephen T. Fletcher,Anne-Marie Broomhall,David Salabert,David Salabert,Sarbani Basu,William J. Chaplin,Yvonne Elsworth,Rafael A. García,Roger New +8 more
TL;DR: In this article, a quasi-biennial (2 year) signal in the natural oscillation frequencies of the Sun was observed and it was shown that the 2 year signal is distinct and separate from, but nevertheless susceptible to the influence of, the main 11 year solar cycle.
References
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Journal ArticleDOI
Cosmical magnetic fields
TL;DR: Magnetic Field Generation in Electrically-Conducting Fluids by H. K. Moffatt as mentioned in this paper is a seminal work in the field of magnetic field generation in electrically conducting fluids.
Journal ArticleDOI
Surface magnetic fields during the solar activity cycle
Robert Howard,Barry J. Labonte +1 more
Abstract: We examine magnetic field measurements from Mount Wilson that cover the solar surface over a 13 1/2 year interval, from 1967 to mid-1980. Seen in long-term averages, the sunspot latitudes are characterized by fields of preceding polarity, while the polar fields are built up by a few discrete flows of following polarity fields. These drift speeds average about 10 m s-1 in latitude - slower early in the cycle and faster later in the cycle - and result from a large-scale poleward displacement of field lines, not diffusion. Weak field plots show essentially the same pattern as the stronger fields, and both data indicate that the large-scale field patterns result only from fields emerging at active region latitudes. The total magnetic flux over the solar surface varies only by a factor of about 3 from minimum to a very strong maximum (1979). Magnetic flux is highly concentrated toward the solar equator; only about 1% of the flux is at the poles. Magnetic flux appears at the solar surface at a rate which is sufficient to create all the flux that is seen at the solar surface within a period of only 10 days. Flux can spread relatively rapidly over the solar surface from outbreaks of activity. This is presumably caused by diffusion. In general, magnetic field lines at the photospheric level are nearly radial.
Journal Article
Spherical alpha-omega-Dynamos by a Variational Method
TL;DR: In this paper, a variational variational expansion method was applied to the kinematic dynamo problem for alpha omega -dynamos, where the modes of free decay in an electrically conducting sphere are used as trial functions.
Journal ArticleDOI
Global Solar Magnetic Fields
TL;DR: The global solar magnetic field greatly affects the corona, heliosphere, and terrestrial environment as well as revealing much about the Sun itself as discussed by the authors, and it may be useful to think of the global field in two ways: as an aggregate of many small scale processes and as an entity.