scholarly journals Rotation Rate of Active Nests on the Sun

1993 ◽  
Vol 141 ◽  
pp. 504-506
Author(s):  
Lidia Van Driel-Gesztelyi ◽  
ED B.J. Van Der Zalm ◽  
Cornelis Zwaan
Keyword(s):  
Solar Cycle ◽  
Short Duration ◽  
Rotation Rate ◽  
The Sun ◽  
Group Position ◽  
Position Data ◽  
Sunspot Groups

AbstractWe analyse Greenwich sunpot group position data for one solar cycle (1952-1963) in order to study the rotation rate of clusters of sunspot groups, so-called active nests. We find that the latitude-dependent rotation rate of nests shows an intrinsic spread. This spread appears to be caused by extensive and dense clusters of sunspot nests (superclusters or nested nests), and by very compact single nests of short duration. The ‘best’ rotation rate is defined as the rate at which the highest number of sunspot groups appear to form nests. This latitude-dependent best rotation is close to the rotation rate of individual recurrent sunspots, although nests seem to rotate slightly more rigidly than sunspot groups.

22-Year Periodicity in the Solar Differential Rotation

2000 ◽  
Vol 179 ◽  
pp. 167-170
Author(s):  
J. Javaraiah
Keyword(s):  
Solar Cycle ◽  
Differential Rotation ◽  
Rotation Rate ◽  
Solar Differential Rotation ◽  
Sunspot Groups

AbstractUsing the data on sunspot groups compiled during 1879–1975, we determined variations in the differential rotation coefficientsAandBduring the solar cycle. The variation in the equatorial rotation rateAis found to be significant only in the odd numbered cycles, with an amplitude ∼ 0.01μrads−1. There exists a good anticorrelation between the variations of the differential rotation rateBderived from the odd and even numbered cycles, suggesting existence of a ‘22-year’ periodicity inB. The amplitude of the variation ofBis ∼ 0.05μrads−1.

scholarly journals Does a Spin–Orbit Coupling Between the Sun and the Jovian Planets Govern the Solar Cycle?

2008 ◽  
Vol 25 (2) ◽  
pp. 85-93 ◽  
Author(s):  
I. R. G. Wilson ◽  
B. D. Carter ◽  
I. A. Waite
Keyword(s):  
Solar Cycle ◽  
Rotation Rate ◽  
Orbital Motion ◽  
Meridional Flow ◽  
Orbit Coupling ◽  
Coupling Mechanism ◽  
The Sun ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Jovian Planets

AbstractWe present evidence to show that changes in the Sun's equatorial rotation rate are synchronized with changes in its orbital motion about the barycentre of the Solar System. We propose that this synchronization is indicative of a spin–orbit coupling mechanism operating between the Jovian planets and the Sun. However, we are unable to suggest a plausible underlying physical cause for the coupling. Some researchers have proposed that it is the period of the meridional flow in the convective zone of the Sun that controls both the duration and strength of the Solar cycle. We postulate that the overall period of the meridional flow is set by the level of disruption to the flow that is caused by changes in Sun's equatorial rotation speed. Based on our claim that changes in the Sun's equatorial rotation rate are synchronized with changes in the Sun's orbital motion about the barycentre, we propose that the mean period for the Sun's meridional flow is set by a Synodic resonance between the flow period (∼22.3 yr), the overall 178.7-yr repetition period for the solar orbital motion, and the 19.86-yr synodic period of Jupiter and Saturn.

scholarly journals Interior Solar-Cycle Changes Detected by Helioseismology

2001 ◽  
Vol 203 ◽  
pp. 40-42 ◽  
Author(s):  
R. Howe ◽  
F. Hill ◽  
R. W. Komm ◽  
J. Christensen-Dalsgaard ◽  
R. Munk Larsen ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Rotation Rate ◽  
Convection Zone ◽  
The Sun

Helioseismic measurements with the MDI instrument aboard SOHO, and complementary measurements from the GONG network, are revealing changes deep within the Sun as the solar cycle progresses. We present results based on recent data from both experiments, including variations in the rotation rate deep inside the convection zone.

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.

Sunspot Groups as Tracers of Sub-Surface Processes

2000 ◽  
Vol 179 ◽  
pp. 155-160
Author(s):  
M. H. Gokhale
Keyword(s):  
Magnetic Flux ◽  
Indian Institute ◽  
Surface Processes ◽  
The Sun ◽  
Global And Local ◽  
Sunspot Groups

AbstractData on sunspot groups have been quite useful for obtaining clues to several processes on global and local scales within the sun which lead to emergence of toroidal magnetic flux above the sun’s surface. I present here a report on such studies carried out at Indian Institute of Astrophysics during the last decade or so.

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.

scholarly journals Solar cycle changes of large-scale solar wind structure

2009 ◽  
Vol 5 (S264) ◽  
pp. 356-358 ◽  
Author(s):  
P. K. Manoharan
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Large Scale ◽  
Interplanetary Space ◽  
The Sun ◽  
Wind Structure ◽  
Level Of Activity ◽  
Solar Wind Structure ◽  
Current Minimum ◽  
Inner Heliosphere

AbstractIn this paper, I present the results on large-scale evolution of density turbulence of solar wind in the inner heliosphere during 1985–2009. At a given distance from the Sun, the density turbulence is maximum around the maximum phase of the solar cycle and it reduces to ~70%, near the minimum phase. However, in the current minimum of solar activity, the level of turbulence has gradually decreased, starting from the year 2005, to the present level of ~30%. These results suggest that the source of solar wind changes globally, with the important implication that the supply of mass and energy from the Sun to the interplanetary space has significantly reduced in the present low level of activity.

scholarly journals Solar-cycle–related Changes in the Helium Ionization Zones of the Sun

2020 ◽  
Vol 903 (2) ◽  
pp. L29
Author(s):  
Courtney B. Watson ◽  
Sarbani Basu
Keyword(s):  
Solar Cycle ◽  
The Sun

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.

scholarly journals Reconstruction of Sun-as-Star Magnetic Field Structure and Evolution Using Filament Observations

1998 ◽  
Vol 167 ◽  
pp. 493-496
Author(s):  
Dmitri I. Ponyavin
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Large Scale ◽  
Solar Magnetic Field ◽  
Close Association ◽  
Field Structure ◽  
The Sun ◽  
Magnetic Field Structure ◽  
Large Scale Magnetic Field ◽  
Field Organization

AbstractA technique is used to restore the magnetic field of the Sun viewed as star from the filament distribution seen on Hα photographs. For this purpose synoptic charts of the large-scale magnetic field reconstructed by the McIntosh method have been compared with the Sun-asstar solar magnetic field observed at Stanford. We have established a close association between the Sun-as-star magnetic field and the mean magnetic field inferred from synoptic magnetic field maps. A filtering technique was applied to find correlations between the Sun-as-star and large-scale magnetic field distributions during the course of a solar cycle. The correlations found were then used to restore the Sun-as-star magnetic field and its evolution in the late 1950s and 1960s, when such measurements of the field were not being made. A stackplot display of the inferred data reveals large-scale magnetic field organization and evolution. Patterns of the Sun-as-star magnetic field during solar cycle 19 were obtained. The proposed technique can be useful for studying the solar magnetic field structure and evolution during times with no direct observations.

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