The unusual minimum of sunspot cycle 23 caused by meridional plasma flow variations

Nandy, Dibyendu; Muñoz-Jaramillo, Andrés; Martens, Petrus C.

doi:10.1038/nature09786

Cited by 148 publications

(121 citation statements)

References 27 publications

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“…The rotation rate of sunspots varies with area and age (Ward 1966;Howard et al 1984;Zappalá & Zuccarello 1991), which has been suggested to be due to the different anchor depths of different types of sunspots (Nesme-Ribes et al 1993;Rhodes et al 1990). Moreover, the differential rotation of all tracers of rotation is also affected by large-and small-scale flows, such as torsional oscillations (Covas et al 2001;Howe et al 2009;Antia & Basu 2010), meridional flows (Javaraiah & Ulrich 2006;Javaraiah 2010;Nandy et al 2011), supergranules (Beck & Schou 2000), etc. Therefore, shortening the fit period reveals the detailed variation of rotation at short time scales, yielding more accurate momentary rotation rates, stronger non-axisymmetries and and a higher accuracy when finding ALs.…”

Section: Discussionmentioning

confidence: 99%

Consistent long-term variation in the hemispheric asymmetry of solar rotation

Zhang

Мурсула

Usoskin

2013

A&A

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Context. Solar active longitudes and their rotation have been studied for a long time using various forms of solar activity. However, the results on the long-term evolution of rotation rates and the hemispheric asymmetry obtained by earlier authors differ significantly from each other. Aims. We aim to find a consistent result on the long-term migration of active longitudes of sunspots in 1877−2008 separately for the two hemispheres. Methods. We used a dynamic, differentially rotating reference system to determine the best-fit values of the differential rotation parameters of active longitudes for each year in 1877−2008. With these parameters we determined the momentary rotation rates at the reference latitude of 17 • and calculated the non-axisymmetries of active longitudes. We repeated this with five different fit intervals and two weighting methods and compared the results. Results. The evolution of solar surface rotation in each hemisphere suggests a quasi-periodicity of about 80−90 years. The long-term variations of solar rotation in the northern and southern hemisphere have a close anti-correlation, leading to a significant 80−90-year quasi-periodicity in the north-south asymmetry of solar rotation. The north-south asymmetry of solar rotation is found to have an inverse relationship with the area of large sunspots. The latitudinal contrast of differential rotation is also found to be anti-correlated with the sunspot area. Different fit and weight methods yield similar results. Conclusions. Our results give strong evidence for the anti-correlation of the rotation of the two solar hemispheres. The long-term oscillation of solar rotation suggests that a systematic interchange of angular momentum takes place between the two hemispheres at a period of about 80−90 years.

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Section: Discussionmentioning

confidence: 99%

Consistent long-term variation in the hemispheric asymmetry of solar rotation

Zhang

Мурсула

Usoskin

2013

A&A

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“…Figure 17 shows that the plumes of decayed active-region flux moving poleward have been of more mixed polarity since the cycle 23 polar reversal than before. One explanation is that the meridional flows are so fast that the leading polarities in the two hemispheres do not have time to interconnect and interact with each other before being swept poleward (e.g., Schrijver and Liu, 2008;Wang et al, 2009;Nandy et al, 2011;Jiang et al, 2013). An alternative explanation is that the active region Joy's law tilts changed their hemispheric bias during cycle 23 (e.g., Jiang et al, 2013;Petrie, 2012).…”

Section: Unusual Cycle 23 Minimummentioning

confidence: 99%

Solar Magnetism in the Polar Regions

Petrie

2015

Living Rev. Sol. Phys.

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This review describes observations of the polar magnetic fields, models for the cyclical formation and decay of these fields, and evidence of their great influence in the solar atmosphere. The polar field distribution dominates the global structure of the corona over most of the solar cycle, supplies the bulk of the interplanetary magnetic field via the polar coronal holes, and is believed to provide the seed for the creation of the activity cycle that follows. A broad observational knowledge and theoretical understanding of the polar fields is therefore an essential step towards a global view of solar and heliospheric magnetic fields. Analyses of both high-resolution and long-term synoptic observations of the polar fields are summarized. Models of global flux transport are reviewed, from the initial phenomenological and kinematic models of Babcock and Leighton to present-day attempts to produce time-dependent maps of the surface magnetic field and to explain polar field variations, including the weakness of the cycle 23 polar fields. The relevance of the polar fields to solar physics extends far beyond the surface layers from which the magnetic field measurements usually derive. As well as discussing the polar fields' role in the interior as seed fields for new solar cycles, the review follows their influence outward to the corona and heliosphere. The global coronal magnetic structure is determined by the surface magnetic flux distribution, and is dominated on large scales by the polar fields. We discuss the observed effects of the polar fields on the coronal hole structure, and the solar wind and ejections that travel through the atmosphere. The review concludes by identifying gaps in our knowledge, and by pointing out possible future sources of improved observational information and theoretical understanding of these fields. Article RevisionsLiving Reviews supports two ways of keeping its articles up-to-date:Fast-track revision. A fast-track revision provides the author with the opportunity to add short notices of current research results, trends and developments, or important publications to the article. A fast-track revision is refereed by the responsible subject editor. If an article has undergone a fast-track revision, a summary of changes will be listed here.Major update. A major update will include substantial changes and additions and is subject to full external refereeing. It is published with a new publication number.For detailed documentation of an article's evolution, please refer to the history document of the article's online version at http://dx

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“…Variation of the flow during the Transition are noteworthy: during solar cycle 23 the meridional flow extended up to the poles while in cycle 22 the circulation had switched equatorward near latitude 60 • (Dikpati et al 2010).The authors suggested that this may have been at the origin of the longer duration of cycle 23. Nandy et al (2011) introduced a fast meridional flow in the first half of the solar polar cycle followed by a slower flow in the second half. It appears that this introduction is able to reproduce the main characteristics of the sunspot cycle 23.…”

Section: Origin Of Pulsationsmentioning

confidence: 99%

“…We refer to papers and reviews by Russell et al (2010), Lockwood et al (2010), Lockwood (2012), Nandy et al (2011), Solanki and Krivova (2011), de Jager andDuhau (2011), de Jager (2012). Quoting Russell et al (2010): "Previous solar minima had occurred in 1996, 1986, 1976 and 1966, so Uncertainty remained at that time, as appears from a quotation by Weiss (2010): Is this just an abnormal fluctuation or are we about to experience a Maunder-like Grand Minimum?…”

Section: Introductionmentioning

confidence: 99%

A Remarkable Recent Transition in the Solar Dynamo

et al. 2016

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We summarize the major aspects of the remarkable, fairly long lasting period (∼ 2005 to ∼ 2010) of low solar activity, that we will call the Transition. It is the transitional stage between the Grand Maximum of the 20th century and a forthcoming (most probably Regular) episode of solar activity. The various kinds of activity in the functioning of the equatorial components of the solar dynamo before and during the Transition are summarized. While the behavior of unipolar magnetic regions and their rest-latitudes already gave very early indications -mid 20th century -of the forthcoming Transition, more such indications became available around 1995 and the main part of it occurred between 2005 and 2010. Some of the inferences are discussed. We submit the hypothesis that the solar tachocline undergoes pulsations and we present some helioseismic evidences. In that scenario we find that its equatorial part has moved downward over a fairly small semi-amplitude (∼ 0.03 solar radii) during the time of the Transition. There are several indications, apart from this 'pulsation', that the tachocline may even be pulsating with still smaller amplitudes in more modes. We speculate about the physical mechanism(s).

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The unusual minimum of sunspot cycle 23 caused by meridional plasma flow variations

Cited by 148 publications

References 27 publications

Consistent long-term variation in the hemispheric asymmetry of solar rotation

Consistent long-term variation in the hemispheric asymmetry of solar rotation

Solar Magnetism in the Polar Regions

A Remarkable Recent Transition in the Solar Dynamo

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