Periodicity and aperiodicity in solar magnetic activity

1990 ◽  
Vol 330 (1615) ◽  
pp. 617-625 ◽  
Keyword(s):  
Magnetic Activity ◽  
Convective Zone ◽  
Magnetic Cycle ◽  
The Past ◽  
Proxy Records ◽  
Solar Magnetic Activity ◽  
Hydromagnetic Dynamo ◽  
Dynamo Waves ◽  
Plausible Theory ◽  
Sunspot Record

Solar activity varies irregularly with an 11-year period whereas the magnetic cycle has a period of 22 years. Similar cycles of activity are seen in other slowly rotating late-type stars. The only plausible theory for their origin ascribes them to a hydromagnetic dynamo operating at, or just below, the base of the convective zone. Linear (kinematic) dynamo models yield strictly periodic solutions with dynamo waves propagating towards or away from the equator. Nonlinear (magnetohydrodynamic) dynamo models allow transitions from periodic to quasi-periodic to chaotic behaviour, as well as loss of spatial symmetry followed by the development of complex spatial structure. Results from simple models can be compared with the observed sunspot record over the past 380 years and with proxy records extending over 9000 years, which show aperiodic modulation of the 11-year cycle.

scholarly journals Deciphering Solar Magnetic Activity: 140 Years Of The ‘Extended Solar Cycle’ – Mapping the Hale Cycle

2021 ◽  
Author(s):  
Scott William McIntosh ◽  
Robert J Leamon ◽  
Ricky Egeland ◽  
Mausumi Dikpati ◽  
Richard C Altrock ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Magnetic Activity ◽  
Magnetic Cycle ◽  
Fundamental Feature ◽  
Superposed Epoch Analysis ◽  
Consistent Picture ◽  
Solar Magnetic Activity ◽  
Epoch Analysis ◽  
Observational Record ◽  
Sunspot Record

Abstract We investigate the occurrence of the ``extended solar cycle'' (ESC) as it occurs in a host observational data spanning 140 years. Investigating coronal, chromospheric, photospheric and interior diagnostics we develop a consistent picture of solar activity migration linked to the 22-year Hale (magnetic) cycle using superposed epoch analysis (SEA) using previously identified Hale cycle termination events as the key time for the SEA. Our analysis shows that the ESC and Hale cycle, as highlighted by the terminator-keyed SEA, is strongly recurrent throughout the entire observational record studied, some 140 years. Applying the same SEA method to the sunspot record confirms that Maunder's butterfly pattern is a subset of the underlying Hale cycle, strongly suggesting that the production of sunspots is not the fundamental feature of the Hale cycle, but the ESC is. The ESC (and Hale cycle) pattern highlights the importance of 55\degree\ latitude in the evolution, and possible production, of solar magnetism.

scholarly journals Deciphering Solar Magnetic Activity: 140 Years of the ‘Extended Solar Cycle’ – Mapping the Hale Cycle

Solar Physics ◽  
2021 ◽  
Vol 296 (12) ◽  
Author(s):  
Scott W. McIntosh ◽  
Robert J. Leamon ◽  
Ricky Egeland ◽  
Mausumi Dikpati ◽  
Richard C. Altrock ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Magnetic Activity ◽  
Magnetic Cycle ◽  
Fundamental Feature ◽  
Superposed Epoch Analysis ◽  
Consistent Picture ◽  
Solar Magnetic Activity ◽  
Epoch Analysis ◽  
Observational Record ◽  
Sunspot Record

AbstractWe investigate the occurrence of the “extended solar cycle” (ESC) as it occurs in a host of observational data spanning 140 years. Investigating coronal, chromospheric, photospheric, and interior diagnostics, we develop a consistent picture of solar activity migration linked to the 22-year Hale (magnetic) cycle using superposed epoch analysis (SEA) and previously identified Hale cycle termination events as the key time for the SEA. Our analysis shows that the ESC and Hale cycle, as highlighted by the terminator-keyed SEA, is strongly recurrent throughout the entire observational record studied, some 140 years. Applying the same SEA method to the sunspot record confirms that Maunder’s butterfly pattern is a subset of the underlying Hale cycle, strongly suggesting that the production of sunspots is not the fundamental feature of the Hale cycle, but the ESC is. The ESC (and Hale cycle) pattern highlights the importance of $55^{\circ }$ 55 ∘ latitude in the evolution, and possible production, of solar magnetism.

Chaotic modulation of the solar cycle

1994 ◽  
Vol 348 (1688) ◽  
pp. 445-447 ◽  
Keyword(s):  
Solar Cycle ◽  
Magnetic Fields ◽  
Active Regions ◽  
17Th Century ◽  
Magnetic Activity ◽  
Maunder Minimum ◽  
Magnetic Cycle ◽  
Sunspot Minimum ◽  
Proxy Records ◽  
Oriented Parallel

The Sun’s magnetic activity varies cyclically, with a well-defined mean period of about 11 years. At the beginning of a new cycle, spots appear at latitudes around ±30°; then the zones of activity expand and drift towards the equator, where they die away as the new cycle starts again at higher latitudes. Active regions are typically oriented parallel to the equator, with oppositely directed magnetic fields in leading and following regions. The sense of these fields is opposite in the two hemispheres and reverses at sunspot minimum. So the magnetic cycle has a 22-year period, with waves of activity that drift towards the equator. Sunspot records show that there was a dearth of spots in the late 17th century - the Maunder minimum - which can also be detected in proxy records.

scholarly journals Reflection of Solar Activity Dynamics in Radionuclide Data

Radiocarbon ◽  
1992 ◽  
Vol 34 (2) ◽  
pp. 207-212 ◽  
Author(s):  
A. V. Blinov ◽  
M. N. Kremliovskij
Keyword(s):  
Nonlinear Dynamics ◽  
Solar Activity ◽  
Numerical Methods ◽  
Chaotic Behavior ◽  
Magnetic Activity ◽  
Data Sets ◽  
Cosmogenic Nuclide ◽  
Proxy Records ◽  
Solar Magnetic Activity ◽  
Activity Dynamics

Variability of solar magnetic activity manifested within sunspot cycles demonstrates features of chaotic behavior. We have analyzed cosmogenic nuclide proxy records for the presence of the solar activity signals. We have applied numerical methods of nonlinear dynamics to the data showing the contribution of the chaotic component. We have also formulated what kind of cosmogenic nuclide data sets are needed for investigations on solar activity.

scholarly journals Global simulations of stellar dynamos

2019 ◽  
Vol 15 (S354) ◽  
pp. 65-85
Author(s):  
G. Guerrero
Keyword(s):  
Magnetic Field ◽  
Spherical Shell ◽  
Ab Initio ◽  
Open Problem ◽  
Magnetic Activity ◽  
Large Eddy Simulations ◽  
The Past ◽  
Large Eddy ◽  
Dynamo Mechanism ◽  
Solar Magnetic Activity

AbstractThe dynamo mechanism, responsible for the solar magnetic activity, is still an open problem in astrophysics. Different theories proposed to explain such phenomena have failed in reproducing the observational properties of the solar magnetism. Thus, ab-initio computational modeling of the convective dynamo in a spherical shell turns out as the best alternative to tackle this problem. In this work we review the efforts performed in global simulations over the past decades. Regarding the development and sustain of mean-flows, as well as mean magnetic field, we discuss the points of agreement and divergence between the different modeling strategies. Special attention is given to the implicit large-eddy simulations performed with the EULAG-MHD code.

scholarly journals Theories of Large Scale Fields and the Magnetic Activity Cycle

1971 ◽  
Vol 43 ◽  
pp. 757-769 ◽  
Author(s):  
N. O. Weiss
Keyword(s):  
Large Scale ◽  
Activity Cycle ◽  
Giant Cells ◽  
Magnetic Activity ◽  
Convective Zone ◽  
Ionized Gas ◽  
Coriolis Forces ◽  
Hydromagnetic Dynamo ◽  
Scale Motion ◽  
The Magnetic Field

The magnetic field is effectively frozen into the ionized gas in the Sun and it is therefore necessary first to describe the motion in the convective zone. Large scale motion in giant cells is strongly affected by Coriolis forces, giving a radial shear in the angular velocity, while the interaction of convection and rotation leads to the equatorial acceleration. Many hydromagnetic dynamo mechanisms have been proposed in the last few years. In particular, meridional fields can be generated from azimuthal fields owing to a preferred sense of helicity in the motionSuch regeneration is included in Leighton's phenomenological model, which reproduces many features of the solar cycle. More detailed models will have to treat the concentration of magnetic flux into ropes by individual convection cells.

scholarly journals Long-term stellar activity: three decades of observations

1996 ◽  
Vol 176 ◽  
pp. 261-268
Author(s):  
R.A. Donahue
Keyword(s):  
Sunspot Cycle ◽  
Magnetic Activity ◽  
Cycle Period ◽  
Cycle Lengths ◽  
Solar Magnetic Activity ◽  
Hydromagnetic Dynamo ◽  
Activity Cycles ◽  
Mean Cycle ◽  
Stellar Magnetic Activity

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.

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