scholarly journals Spectral characteristic of mid-term quasi-periodicities in sunspot data

2019 ◽  
Vol 491 (4) ◽  
pp. 5572-5578 ◽  
Author(s):  
P Frick ◽  
D Sokoloff ◽  
R Stepanov ◽  
V Pipin ◽  
I Usoskin
Keyword(s):  
Solar Activity ◽  
Solar Rotation ◽  
Rotation Period ◽  
Activity Cycle ◽  
Solar Activity Cycle ◽  
Dominant Frequency ◽  
Small Scale ◽  
Quasi Biennial Oscillation ◽  
Solar Radio Flux ◽  
Sunspot Data

ABSTRACT Numerous analyses suggest the existence of various quasi-periodicities in solar activity. The power spectrum of solar activity recorded in sunspot data is dominated by the ∼11-yr quasi-periodicity, known as the Schwabe cycle. In the mid-term range (1 month–11 yr) a pronounced variability known as a quasi-biennial oscillation is widely discussed. In the shorter time-scale a pronounced peak, corresponding to the synodic solar rotation period (∼27 d), is observed. Here we revisit the mid-term solar variability in terms of statistical dynamics of fully turbulent systems, where solid arguments are required to accept an isolated dominant frequency in a continuous (smooth) spectrum. For this, we first undertook an unbiased analysis of the standard solar data, sunspot numbers and the F10.7 solar radio flux index, by applying a wavelet tool, which allows one to perform a frequency–time analysis of the signal. Considering the spectral dynamics of solar activity cycle by cycle, we showed that no single periodicity can be separated, in a statistically significant manner, in the specified range of periods. We examine whether a model of the solar dynamo can reproduce the mid-term oscillation pattern observed in solar data. We found that a realistically observed spectrum can be explained if small spatial (but not temporal) scales are effectively smoothed. This result is important because solar activity is a global feature, although monitored via small-scale tracers like sunspots.

scholarly journals The Observed Relationships Between Some Solar Rotation Parameters and the Activity Cycle

1983 ◽  
Vol 102 ◽  
pp. 99-111
Author(s):  
Robert Howard ◽  
Barry J. LaBonte
Keyword(s):  
Solar Activity ◽  
Solar Rotation ◽  
Rotational Velocity ◽  
Torsional Oscillation ◽  
Periodic Oscillation ◽  
Activity Cycle ◽  
Solar Activity Cycle ◽  
Solar Activity Minimum ◽  
Activity Maximum ◽  
Open Question

Several parameters of the solar rotation show variations which appear to relate to the phase of the solar activity cycle. The latitude gradient of the differential rotation, as seen in the coefficients of the sin2 and sin4 terms in the latitude expansion, shows marked variations with the cycle. One of these variations may be described as a one-cycle-per-hemisphere torsional oscillation with a period of 11 years, where the high latitudes rotate faster at solar activity maximum and slower at minimum, and the low latitudes rotate faster at solar activity minimum and slower at maximum. Another variation is a periodic oscillation of the fractional difference in the low-latitude rotation between north and south hemispheres. The possibility of a variation in the absolute rotational velocity of the sun in phase with the solar cycle remains an open question. The two-cycle-per-hemisphere torsional waves in the solar rotation also represent an aspect of the rotation which varies with the cycle. We show that the amplitude of the fast flowing zone rises a year before the rise to activity maximum. The fast zone seems to be physically the more significant of the two zones.

Investigation of the coronal heating through phase relation of solar activity indexes

2020 ◽  
Vol 37 ◽  
Author(s):  
K. J. Li ◽  
J. C. Xu ◽  
Z. Q. Yin ◽  
J. L. Xie ◽  
W. Feng
Keyword(s):  
Solar Wind ◽  
Solar Activity ◽  
Phase Relation ◽  
Large Scale ◽  
Solar Rotation ◽  
Rotation Period ◽  
Magnetic Activity ◽  
Coronal Heating ◽  
Small Scale

Abstract The coronal heating problem is a long-standing perplexing issue. In this study, 13 solar activity indexes are used to investigate their phase relation with the sunspot number (SSN). Only three of them are found to statistically significantly lag the SSN (large-scale magnetic activity) by about one solar rotation period; the three indexes are total solar irradiance (TSI), the modified coronal index, and the solar wind velocity; the former two indexes may represent the long-term variation of energy quantity of the heated photosphere and corona, respectively. The Mount Wilson Sunspot Index (MWSI) and the Magnetic Plage Strength Index (MPSI), which reflect the large- and small-scale magnetic field activities, respectively, are also utilised to investigate their phase relations with the three indexes. The three indexes are found to be much more intimately related to MPSI than to MWSI, and MWSI statistically significantly leads TSI by about one rotation period. The heated corona is found to pulse perfectly in step with the small-scale magnetic activity rather than the large-scale magnetic activity; furthermore, combined with observations, our statistical evidence should thus attribute coronal heating firmly to small-scale magnetic activity phenomena, such as spicules, micro-flares, nano-flares, and others. The photosphere and the corona are synchronously heated, which should seemingly prefer magnetic reconnection heating to wave heating. In the long term, such a coronal heating way is inferred effective. Statistically, it is also small-scale magnetic activity phenomena that produce TSI enhancement. Coronal heating and solar wind acceleration are found to be synchronous, as standard models require.

scholarly journals Solar activity and differential rotation

2010 ◽  
Vol 6 (S273) ◽  
pp. 298-302
Author(s):  
Hari Om Vats ◽  
Satish Chandra
Keyword(s):  
Solar Activity ◽  
Differential Rotation ◽  
Rotation Rate ◽  
Rotation Period ◽  
Activity Cycle ◽  
Solar Activity Cycle ◽  
X Ray ◽  
Sunspot Numbers ◽  
Sidereal Rotation

AbstractThe coronal sidereal rotation rate as a function of latitude for each year, extending from 1992 to 2001 for soft X-ray images and from 1998 - 2005 for radio images are obtained. The present analysis reveals that the equatorial rotation rate of the corona is comparable to the photosphere and the chromosphere, However, at the higher latitudes, the corona rotation quite differently than the photosphere and chromosphere. The latitude differential obtained by both radio and X-ray images is quite variable throughout the period of the study. The equatorial rotation period seems to vary almost systematically with sunspot numbers which indicates its dependence on the phases of the solar activity cycle.

scholarly journals Systematic regularity of solar coronal rotation during the time interval 1939–2019

2019 ◽  
Vol 491 (1) ◽  
pp. 848-857 ◽  
Author(s):  
L H Deng ◽  
X J Zhang ◽  
H Deng ◽  
Y Mei ◽  
F Wang
Keyword(s):  
Rotation Period ◽  
Phase Relationship ◽  
Activity Cycle ◽  
Solar Activity Cycle ◽  
Magnetic Activity ◽  
Time Interval ◽  
Small Range ◽  
Quasi Biennial Oscillation ◽  
Coronal Rotation ◽  
Solar Coronal

ABSTRACT The temporal variation of solar coronal rotation appears to be very complex and its relevance to the 11-year solar activity cycle is still unclear. Using the modified coronal index for the time interval from 1939 January 1–2019 May 31, the systematic regularities of solar coronal rotation are investigated. Our main findings are as follows. (1) From a global point of view, the synodic coronal rotation period with a value of 27.5 days is the only significant period at periodic scales shorter than 64 days. (2) The coronal rotation period exhibits an obvious decreasing trend during the time interval considered, implying that the solar corona accelerates its global rotation rate in the long run. (3) Significant periods of 3.25, 6.13, 9.53 and 11.13 years exist in coronal rotation, providing evidence that coronal rotation should be connected with the quasi-biennial oscillation, the 11-year solar cycle and the 22-year Hale cycle (or magnetic activity reversal). (4) The phase relationship between the coronal rotation period and solar magnetic activity is not only time-dependent but also frequency-dependent. For a small range around the 11-year cycle band, there is a systematic trend in phase and a small mismatch in this band causes the phase to drift. The possible mechanism for the above analysis results is discussed.

Trends in Parameters of the F2 Layer and the 24th Solar-Activity Cycle

2020 ◽  
Vol 60 (5) ◽  
pp. 586-596 ◽  
Author(s):  
A. D. Danilov ◽  
A. V. Konstantinova
Keyword(s):  
Solar Activity ◽  
Activity Cycle ◽  
Solar Activity Cycle

scholarly journals On the Prediction of Solar Cycles

Solar Physics ◽  
2021 ◽  
Vol 296 (1) ◽  
Author(s):  
V. Courtillot ◽  
F. Lopes ◽  
J. L. Le Mouël
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Transfer Function ◽  
Singular Spectrum Analysis ◽  
Activity Cycle ◽  
Solar Activity Cycle ◽  
Planetary Motion ◽  
Data Sets ◽  
Solar Cycles ◽  
Jovian Planets

AbstractThis article deals with the prediction of the upcoming solar activity cycle, Solar Cycle 25. We propose that astronomical ephemeris, specifically taken from the catalogs of aphelia of the four Jovian planets, could be drivers of variations in solar activity, represented by the series of sunspot numbers (SSN) from 1749 to 2020. We use singular spectrum analysis (SSA) to associate components with similar periods in the ephemeris and SSN. We determine the transfer function between the two data sets. We improve the match in successive steps: first with Jupiter only, then with the four Jovian planets and finally including commensurable periods of pairs and pairs of pairs of the Jovian planets (following Mörth and Schlamminger in Planetary Motion, Sunspots and Climate, Solar-Terrestrial Influences on Weather and Climate, 193, 1979). The transfer function can be applied to the ephemeris to predict future cycles. We test this with success using the “hindcast prediction” of Solar Cycles 21 to 24, using only data preceding these cycles, and by analyzing separately two 130 and 140 year-long halves of the original series. We conclude with a prediction of Solar Cycle 25 that can be compared to a dozen predictions by other authors: the maximum would occur in 2026.2 (± 1 yr) and reach an amplitude of 97.6 (± 7.8), similar to that of Solar Cycle 24, therefore sketching a new “Modern minimum”, following the Dalton and Gleissberg minima.

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