Evolution of sunspot activity and inversion of the Sun’s polar magnetic field in the current cycle

Мордвинов, А. В.; Grigoryev, V. M.; Erofeev, D. V.

doi:10.1016/j.asr.2015.02.013

Cited by 11 publications

(9 citation statements)

References 17 publications

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“…The poleward transport of abnormal UMRs makes related surges of leadingpolarity (Yeates, Baker, and van Driel-Gesztelyi, 2015;Mordvinov, Grigoryev, and Erofeev, 2015;Mordvinov et al, 2016;Lockwood et al, 2017). Leadingpolarity surges are usually associated with large activity complexes nearby or within the domains of negative tilt predominance.…”

Section: Introductionmentioning

confidence: 99%

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

Мордвинов

Kitchatinov

2019

Sol Phys

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Synoptic magnetograms and relevant proxy data were analyzed to study the evolution of the Sun's polar magnetic fields. Time-latitude analysis of large-scale magnetic fields demonstrates cyclic changes in their zonal structure and the polar-field buildup. The time-latitude distributions of the emergent and remnant magnetic flux enable us to examine individual features of recent cycles. The poleward transport of predominantly following polarities contributed much of the polar flux and led to polar-field reversals. Multiple reversals of dominant polarities at the Sun's poles were identified in Cycles 20 and 21. Three-fold reversals were caused by remnant flux surges of following and leading polarities. Time-latitude analysis of solar magnetic fields in Cycles 20-24 revealed zones which are characterized by a predominance of negative (non-Joy's) tilts and appearance of active regions which violate Hale's polarity law. The decay of non-Joy's and anti-Hale's active regions result in remnant flux surges which disturb the usual order in magnetic flux transport and sometimes lead to multiple reversals of polar fields. The analysis of local and large-scale magnetic fields in their causal relation improved our understanding of the Sun's polar field weakening.

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Section: Introductionmentioning

confidence: 99%

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

Мордвинов

Kitchatinov

2019

Sol Phys

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“…Decay of the ACs, that were observed in 2014, caused formation of extended remnant-flux surge, which changed dominant polarity at the south pole. However, this regular picture was disturbed by the leadingpolarity surges which arose after the decay of ARs characterized by non-Joy's law tilts (Yeates, Baker, and van Driel-Gesztelyi, 2015;Mordvinov, Grigoryev, and Erofeev, 2015;Mordvinov et al, 2016).…”

Section: Evolution Of Magnetic Field and Coronal Holes In Cycles 23mentioning

confidence: 99%

Rearrangements of Open Magnetic Flux and Formation of Polar Coronal Holes in Cycle 24

Golubeva

Мордвинов

2017

Sol Phys

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A method of synoptic map assimilation has been developed to study global rearrangements of open magnetic flux and formation of polar coronal holes (PCHs) in the current cycle. The analysis reveals ensembles of coronal holes (ECHs) which appear within unipolar magnetic regions associated with decaying activity complexes (ACs). The cause-effect relations between them explain asynchronous PCH formation observed at the northern and southern hemispheres of the Sun. Thus, the decay of large ACs, that were observed in 2014, led to formation of an extensive ECH, which then became the south PCH in mid-2015. Intricate structure of magnetic fields in the northern polar zone has impeded the north PCH formation, despite the fact that the dominant polarity at the North Pole reversed two years earlier than at the South Pole. The north PCH formed only by mid-2016 as the result of gradual merger of high-latitudinal ECHs associated with several decaying ACs.

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“…Moreover, the comparison between the hemispheres shows that the peak of activity in the south is more intense for all three wavelengths. The stronger southern activity started in the first semester of 2013 and is coincident with the complete polar field reversion of the north pole (Mordvinov et al 2015). Since solar cycle 20, polar field reversals first occurred in the north (Svalgaard & Kamide 2013), all those cycles showed a more intense first peak.…”

Section: Equatorial Regionmentioning

confidence: 99%

Comparison of solar radio and extreme ultraviolet synoptic limb charts during the present solar maximum

Silva¹,

Selhorst²,

Simões³

et al. 2016

A&A

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Aims. The present solar cycle is particular in many aspects: it had a delayed rising phase, it is the weakest of the last 100 yrs, and it presents two peaks separated by more than one year. To understand the impact of these characteristics on the solar chromosphere and coronal dynamics, images from a wide wavelength range are needed. In this work we use the 17 GHz radio continuum, which is formed in the upper chromosphere and the extreme ultraviolet (EUV) lines 304 and 171 Å, that come from the transition region (He ii, T ∼ 6−8 × 10 4 K) and the corona (Fe IX, X, T ∼ 10 6 K), respectively. We extend upon a previous similar analysis, and compare the mean equatorial and polar brightening behavior at radio and EUV wavelengths during the maximum of the present solar cycle, covering the period between 2010 and 2015. Methods. We analyze daily images at 304 and 171 Å obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The 17 GHz maps were obtained by the Nobeyama Radioheliograph (NoRH). To construct synoptic limb charts, we calculated the mean emission of delimited limb areas with 100 wide and angular separation of 5 • . Results. At the equatorial region, the results show a hemispheric asymmetry of the solar activity. The northern hemisphere dominance is coincident with the first sunspot number peak, whereas the second peak occurs concurrently with the increase in the activity at the south. The polar emission reflects the presence of coronal holes at both EUV wavelengths, moreover, the 17 GHz polar brightenings can be associated with the coronal holes. Until 2013, both EUV coronal holes and radio polar brightenings were more predominant at the south pole. Since then they have not been apparent in the north, but thus appear in the beginning of 2015 in the south as observed in the synoptic charts. Conclusions. This work strengthens the association between coronal holes and the 17 GHz polar brightenings as it is evident in the synoptic limb charts in agreement with previous case study papers. The enhancement of the radio brightness in coronal holes is explained by the presence of bright patches closely associated with the presence of intense unipolar magnetic fields. However, observations with better spatial resolution and also at different radio wavelengths will be necessary to fully understand the physical mechanisms that link these features.

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Evolution of sunspot activity and inversion of the Sun’s polar magnetic field in the current cycle

Cited by 11 publications

References 17 publications

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

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

Rearrangements of Open Magnetic Flux and Formation of Polar Coronal Holes in Cycle 24

Comparison of solar radio and extreme ultraviolet synoptic limb charts during the present solar maximum

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