Distribution of Magnetic Bipoles on the Sun Over Three Solar Cycles

The evolution of active regions (AR) from their emergence through their long decay process is of fundamental importance in solar physics. Since large-scale flux is generated by the deepseated dynamo, the observed characteristics of flux emergence and that of the subsequent decay provide vital clues as well as boundary conditions for dynamo models. Throughout their evolution, ARs are centres of magnetic activity, with the level and type of activity phenomena being dependent on the evolutionary stage of the AR. As new flux emerges into a pre-existing magnetic environment, its evolution leads to re-configuration of small-and large-scale magnetic connectivities. The decay process of ARs spreads the once-concentrated magnetic flux over an ever-increasing area. Though most of the flux disappears through small-scale cancellation processes, it is the remnant of large-scale AR fields that is able to reverse the polarity of the poles and build up new polar fields. In this Living Review the emphasis is put on what we have learned from observations, which is put in the context of modelling and simulation efforts when interpreting them. For another, modelling-focused Living Review on the sub-surface evolution and emergence of magnetic flux see Fan (2009). In this first version we focus on the evolution of dominantly bipolar ARs. 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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“…However, the largest ARs again appear to statistically deviate from Joy's law (see Tlatov et al (2010); Figure 11). …”

Section: Tilt Anglementioning

confidence: 96%

“…Recently, Tlatov et al (2010) studied the latitudinal distribution and orientation of magnetic bipoles during cycles 21 -23. The data set included daily observations from Kitt Peak (1975Peak ( -2002 and MDI/SOHO (1996-2009.…”

Section: Tilt Anglementioning

confidence: 99%

Evolution of Active Regions

Driel-Gesztelyi

Green

2015

Living Rev. Sol. Phys.

265

131

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“…3 looks fairly normal and well behaved so we assume that the method used is acceptable. Tlatov & Pevtsov (2013) proposed an interesting idea that the torsional oscillation pattern, associated with rotation velocity residuals, could -at least partially -be an artefact of binning in latitude b. The authors have been successful in simulating the torsional oscillation pattern by assuming drifting of the tracers towards the solar equator during the solar activity cycle.…”

Section: Solar Rotation Profile and Rotation Velocity Residualsmentioning

confidence: 99%

“…We also calculated average latitude,b, instead of using a middle value of b for each bin. This process should alleviate the binning problem described by Tlatov & Pevtsov (2013), because the value ofb is much more appropriate in the case of uneven distribution of data points in the bin.…”

Section: Solar Rotation Profile and Rotation Velocity Residualsmentioning

confidence: 99%

Meridional motions and Reynolds stress from SDO/AIA coronal bright points data

Sudar

Saar

Skokić

et al. 2016

A&A

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Context. It is possible to detect and track coronal bright points (CBPs) in Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) images. A combination of high resolution and high cadence provides a wealth of data that can be used to determine velocity flows on the solar surface with very high accuracy. Aims. We derived a very accurate solar rotation profile and investigated meridional flows, torsional oscillations, and horizontal Reynolds stress based on ≈6 months of SDO/AIA data. Methods. We used a segmentation algorithm to detect CBPs in SDO/AIA images. We also used invariance of the solar rotation profile with central meridian distance (CMD) to determine the height of CBPs in the 19.3 nm channel. Results. The best fit solar rotation profile is given by ω(b) = (14.4060 ± 0.0051 + (−1.662 ± 0.050) sin 2 b + (−2.742 ± 0.081) sin 4 b) • day −1 . The height of CBPs in the SDO/AIA 19.3 nm channel was found to be ≈6500 km. Meridional motion is predominantly poleward for all latitudes, while solar velocity residuals show signs of torsional oscillations. Horizontal Reynolds stress was found to be smaller than in similar works, but still showed transfer of angular momentum towards the solar equator. Conclusions. Most of the results are consistent with Doppler measurements rather than tracer measurements. The fairly small calculated value of horizontal Reynolds stress might be due to the particular phase of the solar cycle. Accuracy of the calculated rotation profile indicates that it is possible to measure changes in the profile as the solar cycle evolves. Analysis of further SDO/AIA CBP data will also provide a better understanding of the temporal behaviour of the rotation velocity residuals, meridional motions, and Reynolds stress.

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“…In the work by Tlatov et al (2010) it was established that the orientation of the magnetic axis of ephemeral areas (ER) depends on the character of large-scale field (Fig. 6).…”

Section: The Fine Structure Of Large-scale Solar Magnetic Fieldmentioning

confidence: 99%

Global magnetic fields: variation of solar minima

Tlatov¹,

Обридко²

2011

Proc. IAU

Self Cite

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Abstract. The topology of the large-scale magnetic field of the Sun and its role in the development of magnetic activity were investigated using Hα charts of the Sun in the period 1887-2011. We have considered the indices characterizing the minimum activity epoch, according to the data of large-scale magnetic fields. Such indices include: dipole-octopole index, area and average latitude of the field with dominant polarity in each hemisphere and others. We studied the correlation between these indices and the amplitude of the following sunspot cycle, and the relation between the duration of the cycle of large-scale magnetic fields and the duration of the sunspot cycle.The comparative analysis of the solar corona during the minimum epochs in activity cycles 12 to 24 shows that the large-scale magnetic field has been slow and steadily changing during the past 130 years. The reasons for the variations in the solar coronal structure and its relation with long-term variations in the geomagnetic indices, solar wind and Gleissberg cycle are discussed.We also discuss the origin of the large-scale magnetic field. Perhaps the large-scale field leads to the generation of small-scale bipolar ephemeral regions, which in turn support the largescale field. The existence of two dynamos: a dynamo of sunspots and a surface dynamo can explain phenomena such as long periods of sunspot minima, permanent dynamo in stars and the geomagnetic field.

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Distribution of Magnetic Bipoles on the Sun Over Three Solar Cycles

Cited by 36 publications

References 18 publications

Evolution of Active Regions

Evolution of Active Regions

Meridional motions and Reynolds stress from SDO/AIA coronal bright points data

Global magnetic fields: variation of solar minima

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