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

Solar Physics ◽  
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.

A Clock in the Sun?

2019 ◽  
Vol 15 (S354) ◽  
pp. 127-133
Author(s):  
C. T. Russell ◽  
J. G. Luhmann ◽  
L. K. Jian
Keyword(s):  
Sunspot Number ◽  
Solar Minimum ◽  
Sunspot Cycle ◽  
Solar Dynamo ◽  
The Sun ◽  
Average Period ◽  
Magnetic Cycle ◽  
Number Cycle ◽  
As If

AbstractThe sunspot cycle is quite variable in duration and amplitude, yet in the long term, it seems to return to solar minimum on schedule, as if guided by a clock with an average period of close to 11.05 years for the sunspot number cycle and 22.1 years for the magnetic cycle. This paper provides a brief review of the sunspot number cycle since 1750, discusses some of the processes controlling the solar dynamo, and provides clues that may add to our understanding of what controls the cadence of the solar clock.

scholarly journals Asteroseismic signatures of magnetic activity variations in solar-type stars

2013 ◽  
Vol 9 (S301) ◽  
pp. 213-216
Author(s):  
Travis S. Metcalfe
Keyword(s):  
Sunspot Cycle ◽  
Magnetic Activity ◽  
The Sun ◽  
Historical Overview ◽  
Solar Type ◽  
Activity Cycles ◽  
Internal Properties

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.

scholarly journals Shapes of stellar activity cycles

2020 ◽  
Vol 638 ◽  
pp. A69
Author(s):  
T. Willamo ◽  
T. Hackman ◽  
J. J. Lehtinen ◽  
M. J. Käpylä ◽  
N. Olspert ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Large Scale ◽  
Magnetic Activity ◽  
The Sun ◽  
Data Set ◽  
Cycle Asymmetry ◽  
Asymmetric Shape ◽  
Activity Cycles ◽  
Magnetohydrodynamic Simulations ◽  
Fast Rise

Context. Magnetic activity cycles are an important phenomenon both in the Sun and other stars. The shape of the solar cycle is commonly characterised by a fast rise and a slower decline, but not much attention has been paid to the shape of cycles in other stars. Aims. Our aim is to study whether the asymmetric shape of the solar cycle is common in other stars as well, and compare the cycle asymmetry to other stellar parameters. We also study the differences in the shape of the solar cycle, depending on the activity indicator that is used. The observations are also compared to simulated activity cycles. Methods. We used the chromospheric Ca II H&K data from the Mount Wilson Observatory HK Project. In this data set, we identified 47 individual cycles from 18 stars. We used the statistical skewness of a cycle as a measure of its asymmetry, and compared this to other stellar parameters. A similar analysis has been performed for magnetic cycles extracted from direct numerical magnetohydrodynamic simulations of solar-type convection zones. Results. The shape of the solar cycle (fast rise and slower decline) is common in other stars as well, although the Sun seems to have particularly asymmetric cycles. Cycle-to-cycle variations are large, but the average shape of a cycle is still fairly well represented by a sinusoid, although this does not take its asymmetry into account. We find only slight correlations between the cycle asymmetry and other stellar parameters. There are large differences in the shape of the solar cycle, depending on the activity indicator that is used. The simulated cycles differ in the symmetry of global simulations that cover the full longitudinal range and are therefore capable of exciting non-axisymmetric large-scale dynamo modes, and wedge simulations that cover a partial extent in longitude, where only axisymmetric large-scale modes are possible. The former preferentially produce positive and the latter negative skewness.

A Stellar Perspective on the Magnetic Future of the Sun

2018 ◽  
Vol 13 (S340) ◽  
pp. 213-216
Author(s):  
Travis S. Metcalfe
Keyword(s):  
Solar Cycle ◽  
Rotation Rate ◽  
Magnetic Transition ◽  
The Sun ◽  
Magnetic Cycle ◽  
Solar Magnetic Cycle ◽  
Mount Wilson Observatory ◽  
Activity Cycles ◽  
Transitional Phase ◽  
Shed Light

AbstractAfter decades of effort, the solar magnetic cycle is exceptionally well characterized, but it remains poorly understood. Pioneering work at the Mount Wilson Observatory demonstrated that other Sun-like stars also show regular activity cycles, and identified two distinct relationships between the rotation rate and the length of the cycle. The solar cycle appears to be an outlier, falling between the two stellar relationships, potentially threatening the very foundation of the solar-stellar connection. Recent discoveries emerging from NASA’s Kepler space telescope have started to shed light on this perplexing result, suggesting that the Sun’s rotation rate and magnetic field are currently in a transitional phase that occurs in all middle-aged stars. We have recently identified the manifestation of this magnetic transition in the best available data on stellar cycles. These observations suggest that the solar cycle is currently growing longer on stellar evolutionary timescales, and that the global dynamo may shut down entirely sometime in the next 0.8-2.4 Gyr. Future tests of this hypothesis will come from ground-based activity monitoring of Kepler targets that span the magnetic transition, and from asteroseismology with the TESS mission to determine precise masses and ages for bright stars with known cycles.

Regression Analysis of Sunspot Numbers for the Solar Cycle 24 in Comparison to Previous Three Cycles

2014 ◽  
Vol 4 (2) ◽  
pp. 477-483
Author(s):  
Debojyoti Halder
Keyword(s):  
Regression Analysis ◽  
Solar Cycle ◽  
Sunspot Number ◽  
The Sun ◽  
Sunspot Numbers ◽  
Solar Cycle 24 ◽  
Current Cycle ◽  
Cycle 24

Sunspots are temporary phenomena on the photosphere of the Sun which appear visibly as dark spots compared to surrounding regions. Sunspot populations usually rise fast but fall more slowly when observed for any particular solar cycle. The sunspot numbers for the current cycle 24 and the previous three cycles have been plotted for duration of first four years for each of them. It appears that the value of peak sunspot number for solar cycle 24 is smaller than the three preceding cycles. When regression analysis is made it exhibits a trend of slow rising phase of the cycle 24 compared to previous three cycles. Our analysis further shows that cycle 24 is approaching to a longer-period but with smaller occurrences of sunspot number.

ESTABLISHING SOLAR ACTIVITY TREND FOR SOLAR CYCLES 21 – 24

2021 ◽  
Vol 44 ◽  
pp. 100-106
Author(s):  
A.K. Singh ◽  
◽  
A. Bhargawa ◽  
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Sunspot Number ◽  
Cosmic Ray ◽  
Occurrence Rate ◽  
The Sun ◽  
Solar Cycles ◽  
Lyman Alpha ◽  
Rate Versus ◽  
Alpha Index

Solar-terrestrial environment is manifested primarily by the physical conditions of solar interior, solar atmosphere and eruptive solar plasma. Each parameter gives unique information about the Sun and its activity according to its defined characteristics. Hence the variability of solar parameters is of interest from the point of view of plasma dynamics on the Sun and in the interplanetary space as well as for the solar-terrestrial physics. In this study, we have analysed various solar transients and parameters to establish the recent trends of solar activity during solar cycles 21, 22, 23 and 24. The correlation coefficients of linear regression of F10.7 cm index, Lyman alpha index, Mg II index, cosmic ray intensity, number of M & X class flares and coronal mass ejections (CMEs) occurrence rate versus sunspot number was examined for last four solar cycles. A running cross-correlation method has been used to study the momentary relationship among the above mentioned solar activity parameters. Solar cycle 21 witnessed the highest value of correlation for F10.7 cm index, Lyman alpha index and number of M-class and X-class flares versus sunspot number among all the considered solar cycles which were 0.979, 0.935 and 0.964 respectively. Solar cycle 22 recorded the highest correlation in case of Mg II index, Ap index and CMEs occurrence rate versus sunspot number among all the considered solar cycles (0.964, 0.384 and 0.972 respectively). Solar cycle 23 and 24 did not witness any highest correlation compared to solar cycle 21 and 22. Further the record values (highest value compared to other solar three cycles) of each solar activity parameters for each of the four solar cycles have been studied. Here solar cycle 24 has no record text at all, this simply indicating that this cycle was a weakest cycle compared to the three previous ones. We have concluded that in every domain solar 24 was weaker to its three predecessors.

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 The Rotational Modulation of Ca II K in the Sun

1991 ◽  
Vol 130 ◽  
pp. 266-267
Author(s):  
I. Sattarov ◽  
A. Hojaev
Keyword(s):  
Solar Cycle ◽  
Active Regions ◽  
Magnetic Activity ◽  
Astronomical Observatory ◽  
Rigid Rotation ◽  
Longitudinal Distribution ◽  
The Sun ◽  
K Index ◽  
Rotational Modulation ◽  
Line Core

The most widely used indicator of the stellar magnetic activity is the flux in the CaII K-line core (K-index) (Baliunas and Vaughan, 1985). The K-index data have also been used for measuring the rotation of stars. But using the method for the Sun gives different results (Keil and Worden, 1984; Singh and Livingston, 1987). The reason for the observed differences, besides those indicated by Singh and Livingston, may be the character of the distribution of active regions. This study is based on observations made at Tashkent Astronomical Observatory and the data published in SGD for solar cycle 21. We study the longitudional distribution of sunspots and plages. Some intervals of active longitudes (IAL) were selected and the evolution of them was studied. Active regions were found to concentrate in certain longitude intervals which are in nearly rigid rotation. Fig. 1 shows the longitudinal distribution of sunspots areas for 1983-84, as an example.

scholarly journals The future of helioseismology

2009 ◽  
Vol 5 (H15) ◽  
pp. 352-353
Author(s):  
Alexander G. Kosovichev
Keyword(s):  
Solar Cycle ◽  
Physical Properties ◽  
Active Regions ◽  
Magnetic Activity ◽  
Solar Dynamo ◽  
Current Status ◽  
The Sun ◽  
Interior Structure ◽  
Structure And Dynamics ◽  
Solar Magnetic Activity

AbstractHelioseismology has provided us with the unique knowledge of the interior structure and dynamics of the Sun, and the variations with the solar cycle. However, the basic mechanisms of solar magnetic activity, formation of sunspots and active regions are still unknown. Determining the physical properties of the solar dynamo, detecting emerging active regions and observing the subsurface dynamics of sunspots are among the most important and challenging problems. The current status and perspectives of helioseismology are briefly discussed.

scholarly journals Apparent solar diameter and variability

1997 ◽  
Vol 181 ◽  
pp. 265-273 ◽  
Author(s):  
A. Vigouroux
Keyword(s):  
Time Series ◽  
Solar Cycle ◽  
Sunspot Number ◽  
Solar Physics ◽  
The Sun ◽  
Solar Diameter ◽  
Total Irradiance ◽  
Pertinent Information

Philippe Delache brought me to solar physics in late June 1992. The first things he began with was the diameter of the Sun as it is measured at the “plateau de Calern”, and my first work was to analyze this time series in order to separate the “noise” from the pertinent information (section 2). Wet then applied the technique developed for this purpose to the study of the 11-year solar cycle as seen in the Wolf sunspot number (section 3) and I continued in collaboration with Judit Pap with the study of total irradiance and some other solar indicators which could help to understand its variations (section 4).

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