Evolution of the Sun’s Polar Fields and the Poleward Transport of Remnant Magnetic Flux

Мордвинов, А. В.; Kitchatinov, L. L.

doi:10.1007/s11207-019-1410-1

Cited by 24 publications

(15 citation statements)

References 83 publications

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“…On comparing the results from Makarov & Sivaraman (1986b), we find that our values of the timings of the polarity reversals are very close to their values. Further, in agreement with Makarov & Sivaraman (1986b) Cycles 16 and 19 had triple polarity reversals for the northern hemisphere, which was also seen in Cycles 20 and 21 (Mordvinov & Kitchatinov 2019).…”

Section: Resultssupporting

confidence: 88%

Long-Term Evolution of the Sun's magnetic field during Cycles 15--19 based on their proxies from Kodaikanal Solar Observatory

Mordvinov,

Karak,

Banerjee

et al. 2020

Preprint

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The regular observation of the solar magnetic field is available only for about last five cycles. Thus, to understand the origin of the variation of the solar magnetic field, it is essential to reconstruct the magnetic field for the past cycles, utilizing other datasets. Long-term uniform observations for the past 100 years as recorded at the Kodaikanal Solar Observatory (KoSO) provide such opportunity. We develop a method for the reconstruction of the solar magnetic field using the synoptic observations of the Sun's emission in the Ca II K and Hα lines from KoSO for the first time. The reconstruction method is based on the facts that the Ca II K intensity correlates well with the unsigned magnetic flux, while the sign of the flux is derived from the corresponding Hα map which provides the information of the dominant polarities. Based on this reconstructed magnetic map, we study the evolution of the magnetic field in Cycles 15-19. We also study bipolar magnetic regions (BMRs) and their remnant flux surges in their causal relation. Time-latitude analysis of the reconstructed magnetic flux provides an overall view of magnetic field evolution: emergent magnetic flux, its further transformations with the formation of unipolar magnetic regions (UMRs) and remnant flux surges. We identify the reversals of the polar field and critical surges of following and leading polarities. We found that the poleward transport of opposite polarities led to multiple changes of the dominant magnetic polarities in poles. Furthermore, the remnant flux surges that occur between adjacent 11-year cycles reveal physical connections between them.

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Section: Resultssupporting

confidence: 88%

Long-Term Evolution of the Sun's magnetic field during Cycles 15--19 based on their proxies from Kodaikanal Solar Observatory

Mordvinov,

Karak,

Banerjee

et al. 2020

Preprint

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“…Triple, or, in common, multiple reversals seem to take place due to appearance of active regions whose polarity is opposite to the usual (according to the Hale's law) hemispheric polarity in the cycle and their further migration to the pole (Mordvinov and Kitchatinov, 2019). Violations of the evolution of polar fields, including short-term polarity reversals, can also be caused by poleward transport of magnetic flux from active regions with negative (non-Joy's) tilts.…”

Section: Discussionmentioning

confidence: 99%

On Polar Magnetic Field Reversal in Solar Cycles 21, 22, 23, and 24

Pishkalo

2019

Sol Phys

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The Sun's polar magnetic fields change their polarity near the maximum of sunspot activity. We analyzed the polarity reversal epochs in Solar Cycles 21 to 24. There were a triple reversal in the N-hemisphere in Solar Cycle 24 and single reversals in the rest of cases. Epochs of the polarity reversal from measurements of the Wilcox Solar Observatory (WSO) are compared with ones when the reversals were completed in the N-and S-hemispheres. The reversal times were compared with hemispherical sunspot activity and with the Heliospheric Current Sheet (HCS) tilts, too. It was found that reversals occurred at the epoch of the sunspot activity maximum in Cycles 21 and 23, and after the corresponding maxima in Cycles 22 and 24, and one-two years after maximal HCS tilts calculated in WSO. Reversals in Solar Cycles 21, 22, 23, and 24 were completed first in the N-hemisphere and then in the S-hemisphere after 0.6, 1.1, 0.7, and 0.9 years, respectively. The polarity inversion in the near-polar latitude range ±(55-90)˚ occurred from 0.5 to 2.0 years earlier that the times when the reversals were completed in corresponding hemisphere. Using the maximal smoothed WSO polar field as precursor we estimated that amplitude of Solar Cycle 25 will reach 116±12 in values of smoothed monthly sunspot numbers and will be comparable with the current cycle amplitude equaled to 116.4.

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“…The magnetic activity of Sun is not identical in two hemispheresthere is always an asymmetry. This hemispheric asymmetry, also called the north-south asymmetry, has been observed in the photospheric magnetic field (Mordvinov & Kitchatinov 2004;McIntosh et al 2013;Mordvinov & Kitchatinov 2019) as well as in many proxies of the solar activity (Mandal et al 2017;Goel & Choudhuri 2009;Norton et al 2014;Mordvinov et al 2020). The hemispheric asymmetry is a real feature of the solar cycle and is not an artefact of inaccurate or noisy observations (Carbonell et al 1993).…”

Section: Introductionmentioning

confidence: 91%

Is the Hemispheric Asymmetry of Monthly Sunspot Area an Irregular Process with Long-Term Memory?

Das,

Ghosh,

Karak

2021

Preprint

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The hemispheric asymmetry of the sunspot cycle is a real feature of the Sun. However, its origin is still not well understood. Here we perform nonlinear time series analysis of the sunspot area (and number) asymmetry to explore its dynamics. By measuring the correlation dimension of the sunspot area asymmetry, we conclude that there is no strange attractor in the data. Further computing Higuchi's dimension, we conclude that the hemispheric asymmetry is largely governed by stochastic noise. However, the behaviour of Hurst exponent reveals that the time series is not completely determined by a memory-less stochastic noise, rather there is a long-term persistence, which can go beyond two solar cycles. Therefore, our study suggests that the hemispheric asymmetry of the sunspot cycle is predominantly originated due to some irregular process in the solar dynamo. The long-term persistence in the solar cycle asymmetry suggests that the solar magnetic field has some memory in the convection zone.

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Evolution of the Sun’s Polar Fields and the Poleward Transport of Remnant Magnetic Flux

Cited by 24 publications

References 83 publications

Long-Term Evolution of the Sun's magnetic field during Cycles 15--19 based on their proxies from Kodaikanal Solar Observatory

Long-Term Evolution of the Sun's magnetic field during Cycles 15--19 based on their proxies from Kodaikanal Solar Observatory

On Polar Magnetic Field Reversal in Solar Cycles 21, 22, 23, and 24

Is the Hemispheric Asymmetry of Monthly Sunspot Area an Irregular Process with Long-Term Memory?

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