Study of Long-Term Variations in Hemispheric Asymmetry of Solar Activity

2018 ◽  
Vol 13 (S340) ◽  
pp. 259-260
Author(s):  
B. Ravindra ◽  
J. Javaraiah
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Hemispheric Asymmetry ◽  
Sunspot Area ◽  
Sunspot Activity ◽  
Phase Lag ◽  
Double Peak ◽  
Northern And Southern Hemispheres ◽  
Long Term Variations

AbstractSunspot activity exhibits hemispheric asymmetry. We study the long-term variations in the hemispheric sunspot area from Kodaikanal white-light data during 1921 – 2011. The results on the presence or absence of double peak in an individual solar cycle, dominant hemispheric activity, and phase lag between the activities of northern and southern hemispheres, etc., are presented.

scholarly journals The origin of parity changes in the solar cycle

2019 ◽  
Vol 489 (3) ◽  
pp. 4329-4337 ◽  
Author(s):  
Soumitra Hazra ◽  
Dibyendu Nandy
Keyword(s):  
Solar Cycle ◽  
Hemispheric Asymmetry ◽  
Sunspot Cycle ◽  
Dynamo Model ◽  
Sunspot Activity ◽  
Cycle Period ◽  
Causal Pathways ◽  
Random Fluctuations ◽  
Simulated Time

ABSTRACT Although sunspots have been systematically observed on the Sun’s surface over the last four centuries, their magnetic properties have been revealed and documented only since the early 1900s. Sunspots typically appear in pairs of opposite magnetic polarities which have a systematic orientation. This polarity orientation is opposite across the equator – a trend that has persisted over the last century. Taken together with the configuration of the global poloidal field of the Sun – this phenomena is consistent with the dipolar parity state of an underlying magnetohydrodynamic dynamo. Although transient hemispheric asymmetry in sunspot emergence is observed, a global parity shift has never been observed. We simulate hemispheric asymmetry through introduction of random fluctuations in a computational dynamo model of the solar cycle and demonstrate that changes in parity are indeed possible in long-term simulations covering thousands of years. Quadrupolar modes are found to exist over significant fraction of the simulated time. In particular, we find that a parity shift in the underlying nature of the sunspot cycle is more likely to occur when sunspot activity dominates in any one hemisphere for a time which is significantly longer than the cycle period. We establish causal pathways connecting hemispheric asymmetry to parity flips mediated via a decoupling of the dynamo cycle period across the two solar hemispheres. Our findings indicate that the solar cycle may have resided in quadrupolar parity states in the past, and provides a possible pathway for predicting parity flips in the future.

Cosmic-ray long-term variations due to the solar activity for the 22nd solar cycle

1995 ◽  
Vol 16 (9) ◽  
pp. 245-248 ◽  
Author(s):  
L. Marmatsouri ◽  
A. Vassilaki ◽  
H. Mavromichalaki ◽  
B. Petropoulos
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Cosmic Ray ◽  
Long Term Variations

The cause of the appearance or disappearance of the Rieger-type periodicity in the northern and southern hemispheres of the sun

2021 ◽  
Vol 38 ◽  
Author(s):  
N. B. Xiang ◽  
X. H. Zhao ◽  
F. Y. Li
Keyword(s):  
Solar Cycle ◽  
Sunspot Area ◽  
Solar Cycles ◽  
Sunspot Maximum ◽  
Royal Observatory ◽  
Rotation Parameters ◽  
The Mean ◽  
Two Parameters ◽  
Northern And Southern Hemispheres

Abstract We use a continuous wavelet transform to analyse the daily hemispheric sunspot area data from the Greenwich Royal Observatory during cycles 12–24 and then study the cause of the appearance or disappearance of the Rieger-type periodicity in the northern and southern hemispheres during a certain cycle. The Rieger-type periodicity in the northern and southern hemispheres should be developed independently in the two hemispheres. This periodicity in the northern hemisphere is generally anti-correlated with the long-term variations in the mean solar cycle strength of hemispheric activity, but the correlation of the two parameters in the southern hemisphere shows a weak correlation. The appearance or disappearance of Rieger-type periodicity in the northern and southern hemispheres during a certain solar cycle is not directly correlated with their corresponding hemispheric mean activity strength but should be related to the strength of the hemispheric activity during sunspot maximum times, which hints the Rieger-type periodicity is more related to temporal evolution of toroidal magnetic field. The Rieger-type periodicity in the two hemispheres disappears in those solar cycles with relatively weak hemispheric activity during sunspot maximum times. The reason for the disappearance of this periodicity may be due to the combined influence of relatively weak toroidal magnetic fields and torsional oscillations, the differential rotation parameters vary through the solar cycle and may not remain more or less unchanged during some time, which does not permit the strong growth of magnetic Rossby waves.

A Study of Variation of the 11-yr Solar Cycle before the onset of the Spoerer Minimum based on Annually measured 14C Content in tree Rings

Radiocarbon ◽  
2019 ◽  
Vol 61 (6) ◽  
pp. 1749-1754 ◽  
Author(s):  
Toru Moriya ◽  
Hiroko Miyahara ◽  
Motonari Ohyama ◽  
Masataka Hakozaki ◽  
Mirei Takeyama ◽  
...  
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Cycle Length ◽  
Detailed Mechanism ◽  
Grand Minimum ◽  
The Past ◽  
Shimokita Peninsula ◽  
Solar Cycle Length ◽  
Long Term Variations

ABSTRACTProxy-based observations of solar activity in the past have revealed long-term variations, such as the Gleissberg cycle (~88 yr), de Vries cycle (~200 yr), and the Hallstatt cycle (~2000 yr). Such long-term variations of solar activity sometimes cause the disappearance of sunspots for several decades. Currently, solar activity is becoming weaker, and there is a possibility that another long-term sunspot minimum could occur. However, the detailed mechanism of the weakening in solar activity is unknown, and the prediction of solar activity is ambiguous. In this study, we investigate the transitions of solar cycle length before the onset of the Spoerer Minimum, the longest grand minimum in the past 2000 yr. We measured the 14C content in an asunaro tree (Thujopsis dolabrata) excavated at Shimokita Peninsula from 1368–1420 CE using the compact AMS system at Yamagata University. It is found that the solar cycle lengthened to be 14–16 yr from 2 cycles before the onset of the Spoerer Minimum.

scholarly journals Evidence of a strong relationship between hemispheric asymmetry in solar coronal rotation and solar activity during solar cycle 24

2020 ◽  
Vol 499 (4) ◽  
pp. 5442-5446
Author(s):  
Jaidev Sharma ◽  
Anil K Malik ◽  
Brajesh Kumar ◽  
Hari Om Vats
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Rotation Rate ◽  
Hemispheric Asymmetry ◽  
Solar Rotation ◽  
Strong Relationship ◽  
Space Mission ◽  
Asymmetry Index ◽  
Coronal Rotation ◽  
Solar Coronal

ABSTRACT In this paper, we report evidence of a very strong and statistically significant relationship between hemispheric asymmetry in the solar coronal rotation rate and solar activity. Our approach is based on the cross-correlation of the hemispheric asymmetry index (AI) in the rotation rate with annual solar activity indicators. To obtain the hemispheric asymmetry in the solar rotation rate, we use solar full disc (SFD) images at 30.4-, 19.5- and 28.4-nm wavelengths for the 24th solar cycle, that is, for the period from 2008 to 2018, as recorded by the Solar Terrestrial Relations Observatory (STEREO) space mission. Our analysis shows that the hemispheric asymmetry in rotation rate is high during the solar maxima from 2011 to 2014. However, hemispheric asymmetry decreases gradually on both sides (i.e. from 2008 to 2011 and from 2014 to 2018). The results show that the AI leads sunspot numbers by ∼ 1.56 yr. This is a clear indication that hemispheric asymmetry triggers the formation of sunspots in conjunction with the differential rotation of the Sun.

scholarly journals North-south asynchrony and long-term variations of sunspot latitudes

2008 ◽  
Vol 4 (S259) ◽  
pp. 237-238 ◽  
Author(s):  
Nadezhda V. Zolotova ◽  
D. I. Ponyavin
Keyword(s):  
Sunspot Area ◽  
Magnetic Equator ◽  
Phase Component ◽  
Long Period ◽  
The North ◽  
Sign Change ◽  
The Mean ◽  
South Asymmetry ◽  
Northern And Southern Hemispheres

AbstractThe long-term records of sunspot area available separately for Northern and Southern Hemispheres have been investigated by means of cross-recurrence technique. Phase component of the north-south asymmetry was extracted. This measure demonstrates long-period systematic variations with the sign change of hemispheric leading in 1930s and 1960s. Moreover phase north-south asynchrony anticorrelates with the so called magnetic equator, which was defined as difference of the mean sunspot latitudes between two hemispheres. Relationships of the phase north-south asynchrony, magnetic equator and butterfly diagrams are presented and discussed.

scholarly journals Long-Term Variations of Solar Differential Rotation and Sunspot Activity: Revisited

Solar Physics ◽  
2013 ◽  
Vol 289 (3) ◽  
pp. 759-768 ◽  
Author(s):  
K. J. Li ◽  
W. Feng ◽  
X. J. Shi ◽  
J. L. Xie ◽  
P. X. Gao ◽  
...  
Keyword(s):  
Differential Rotation ◽  
Sunspot Activity ◽  
Solar Differential Rotation ◽  
Long Term Variations

scholarly journals Solar Modulation Effects in Terrestrial Production of Carbon-14

Radiocarbon ◽  
1980 ◽  
Vol 22 (2) ◽  
pp. 133-158 ◽  
Author(s):  
Giuliana Castagnoli ◽  
Devendra Lal
Keyword(s):  
Solar Activity ◽  
Cosmic Ray ◽  
Solar Modulation ◽  
Carbon 14 ◽  
Cosmic Ray Modulation ◽  
The Earth ◽  
Secular Variations ◽  
Galactic Cosmic Ray ◽  
Long Term Variations

This paper is concerned with the expected deviations in the production rate of natural 14C on the earth due to changes in solar activity. We review the published estimates of the global production rates of 14C due to galactic and solar cosmic ray particles, and present new estimates of the expected secular variations in 14C production, taking into account the latest information available on galactic cosmic ray modulation and long-term variations in solar activity.

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