Double sunspot-cycle variation in terrestrial magnetic activity, 1884-1963

AbstractObservations of magnetic activity cycles in other stars provide a broader context for our understanding of the 11-year sunspot cycle. The discovery of short activity cycles in a few stars, and the recognition of analogous variability in the Sun, suggest that there may be two distinct dynamos operating in different regions of the interior. Consequently, there is a natural link between studies of magnetic activity and asteroseismology, which can characterize some of the internal properties that are relevant to dynamos. I provide a brief historical overview of the connection between these two fields (including prescient work by Wojtek Dziembowski in 2007), and I highlight some exciting results that are beginning to emerge from the Kepler mission.

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Long-term stellar activity: three decades of observations

Symposium - International Astronomical Union ◽

10.1017/s0074180900083285 ◽

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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A 22-year cycle in the F layer ionization of the ionosphere

Annales Geophysicae ◽

10.1007/s00585-997-1015-0 ◽

1997 ◽

Vol 15 (8) ◽

pp. 1015-1027 ◽

Cited By ~ 9

Author(s):

E. Feichter ◽

R. Leitinger

Keyword(s):

Solar Activity ◽

Geomagnetic Activity ◽

Annual Variation ◽

Sunspot Cycle ◽

Statistical Processing ◽

High Solar Activity ◽

Electron Content ◽

Solar Cycles ◽

Total Electron ◽

Cycle Variation

Abstract. The double-sunspot-cycle variation in terrestrial magnetic activity has been well known for about 30 years. In 1990 we examined and compared the low-solar-activity (LSA) part of two consecutive cycles and predicted from this database and from published results the existence of a double-sunspot-cycle variation in total electron content (TEC) of the ionosphere too. This is restricted to noontime when the semi-annual component is well developed. Since 1995 we have had enough data for the statistical processing for high-solar-activity (HSA) conditions of two successive solar cycles. The results confirm the LSA findings. The annual variation of TEC shows a change from an autumn maximum in cycle 21 to a spring maximum during the next solar cycle. Similar to the aa indices for geomagnetic activity the TEC data show a phase change in the 1-year component of the Fourier transform of the annual variation. Additionally we found the same behaviour in the F-layer peak electron density (Nmax) over four solar cycles. This indicates that there exists a double-sunspot-cycle variation in the F-layer ionization over Europe too. It is very likely coupled with the 22-year cycle in geomagnetic activity.

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Overlapping Magnetic Activity Cycles and the Sunspot Number: Forecasting Sunspot Cycle 25 Amplitude

Solar Physics ◽

10.1007/s11207-020-01723-y ◽

2020 ◽

Vol 295 (12) ◽

Author(s):

Scott W. McIntosh ◽

Sandra Chapman ◽

Robert J. Leamon ◽

Ricky Egeland ◽

Nicholas W. Watkins

Keyword(s):

Solar Cycle ◽

Sunspot Number ◽

Sunspot Cycle ◽

Periodic Variation ◽

Magnetic Activity ◽

The Sun ◽

Magnetic Cycle ◽

Hilbert Transforms ◽

Observational Astronomy ◽

Activity Cycles

AbstractThe Sun exhibits a well-observed modulation in the number of spots on its disk over a period of about 11 years. From the dawn of modern observational astronomy, sunspots have presented a challenge to understanding—their quasi-periodic variation in number, first noted 175 years ago, has stimulated community-wide interest to this day. A large number of techniques are able to explain the temporal landmarks, (geometric) shape, and amplitude of sunspot “cycles,” however, forecasting these features accurately in advance remains elusive. Recent observationally-motivated studies have illustrated a relationship between the Sun’s 22-year (Hale) magnetic cycle and the production of the sunspot cycle landmarks and patterns, but not the amplitude of the sunspot cycle. Using (discrete) Hilbert transforms on more than 270 years of (monthly) sunspot numbers we robustly identify the so-called “termination” events that mark the end of the previous 11-yr sunspot cycle, the enhancement/acceleration of the present cycle, and the end of 22-yr magnetic activity cycles. Using these we extract a relationship between the temporal spacing of terminators and the magnitude of sunspot cycles. Given this relationship and our prediction of a terminator event in 2020, we deduce that sunspot Solar Cycle 25 could have a magnitude that rivals the top few since records began. This outcome would be in stark contrast to the community consensus estimate of sunspot Solar Cycle 25 magnitude.

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Structure of the extended solar magnetic field and the sunspot cycle variation in cosmic ray intensity

Nature ◽

10.1038/262766a0 ◽

1976 ◽

Vol 262 (5571) ◽

pp. 766-768 ◽

Cited By ~ 73

Author(s):

LEIF SVALGAARD ◽

JOHN M. WILCOX

Keyword(s):

Magnetic Field ◽

Solar Magnetic Field ◽

Sunspot Cycle ◽

Cosmic Ray ◽

Cosmic Ray Intensity ◽

Cycle Variation

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Global magnetic fields: variation of solar minima

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312004723 ◽

2011 ◽

Vol 7 (S286) ◽

pp. 113-122

Author(s):

Andrey G. Tlatov ◽

Vladimir N. Obridko

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Large Scale ◽

Sunspot Cycle ◽

Magnetic Activity ◽

Small Scale ◽

The Sun ◽

Large Scale Magnetic Field ◽

Scale Field ◽

Large Scale Field

AbstractThe topology of the large-scale magnetic field of the Sun and its role in the development of magnetic activity were investigated using Hα charts of the Sun in the period 1887-2011. We have considered the indices characterizing the minimum activity epoch, according to the data of large-scale magnetic fields. Such indices include: dipole-octopole index, area and average latitude of the field with dominant polarity in each hemisphere and others. We studied the correlation between these indices and the amplitude of the following sunspot cycle, and the relation between the duration of the cycle of large-scale magnetic fields and the duration of the sunspot cycle.The comparative analysis of the solar corona during the minimum epochs in activity cycles 12 to 24 shows that the large-scale magnetic field has been slow and steadily changing during the past 130 years. The reasons for the variations in the solar coronal structure and its relation with long-term variations in the geomagnetic indices, solar wind and Gleissberg cycle are discussed.We also discuss the origin of the large-scale magnetic field. Perhaps the large-scale field leads to the generation of small-scale bipolar ephemeral regions, which in turn support the large-scale field. The existence of two dynamos: a dynamo of sunspots and a surface dynamo can explain phenomena such as long periods of sunspot minima, permanent dynamo in stars and the geomagnetic field.

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