Long-term variations in the sunspot magnetic fields and bipole properties from 1918 to 2014

Tlatova, K. A.; Vasil’eva, V. V.; Pevtsov, Alexei A.

doi:10.1134/s0016793215070233

Cited by 12 publications

(9 citation statements)

References 14 publications

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“…The data cover a century long period. The original MWO drawings were digitized using software package developed by Tlatova et al (2015), see also references therein. The digitization includes the date and time of observations, heliographic coordinates of each umbra, its area, the strength, and polarity of its magnetic field.…”

Section: Comparison With Observations Of the Mean Tiltmentioning

confidence: 99%

“…In spite of various theoretical, numerical and observational studies related to the mean tilt (DSilva & Choudhuri 1993;Kosovichev & Stenflo 2008;Dasi-Espuig et al 2010;McClintock & Norton 2013;Tlatov et al 2013;Illarionov et al 2015;Tlatov 2015;Tlatova et al 2015), some observational features related to the mean tilt of sunspot bipolar regions are not explained. As follows from observations (Tlatova et al 2018), the latitudinal dependence of the mean tilt of sunspot bipolar regions can deviate from sin φ.…”

Section: Introductionmentioning

confidence: 99%

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The mean tilt of sunspot bipolar regions: theory, simulations and comparison with observations

Kleeorin,

Safiullin,

Kuzanyan

et al. 2020

Preprint

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A theory of the mean tilt of sunspot bipolar regions (the angle between a line connecting the leading and following sunspots and the solar equator) is developed. A mechanism of formation of the mean tilt is related to the effect of Coriolis force on meso-scale motions of super-granular convection and large-scale meridional circulation. The balance between the Coriolis force and the Lorentz force (the magnetic tension) determines an additional contribution caused by the large-scale magnetic field to the mean tilt of the sunspot bipolar regions at low latitudes. The latitudinal dependence of the solar differential rotation affects the mean tilt which can explain deviations from the Joy's law for the sunspot bipolar regions at high latitudes. The obtained theoretical results and performed numerical simulations based on the nonlinear mean-field dynamo theory which takes into account conservation of the total magnetic helicity and the budget equation for the evolution of the Wolf number density, are in agreement with observational data of the mean tilt of sunspot bipolar regions over individual solar cycles 15 -24.

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Section: Comparison With Observations Of the Mean Tiltmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The mean tilt of sunspot bipolar regions: theory, simulations and comparison with observations

Kleeorin,

Safiullin,

Kuzanyan

et al. 2020

Preprint

View full text Add to dashboard Cite

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“…To keep track of future modifications to the original digitized dataset, we introduce the version number. The results of the initial digitization already published in some early papers (e.g., Tlatova et al 2015Tlatova et al , 2018 are designated as version MWO_SPOTS_20171101, where the numbers represent the year, month, and day of last changes to the dataset. The current version of the dataset described in this paper is MWO_SPOTS_20180801.…”

Section: Errors and Uncertainties From Digitizationmentioning

confidence: 99%

“…In the mid-2000s to early 2010s, a series of papers related to the long-term variation of sunspot field strengths rejuvenated the interest in the MWO synoptic dataset (Penn & Livingston 2006Pevtsov et al 2011Pevtsov et al , 2014Watson et al 2011;Rezaei et al 2012Rezaei et al , 2015Nagovitsyn et al 2012;Livingston et al 2012;Lockwood et al 2014;Tlatova et al 2015). This renewed interest led to our present collaborative effort in digitizing the Mount Wilson sunspot drawings.…”

Section: Introductionmentioning

confidence: 97%

Reconstructing solar magnetic fields from historical observations

Pevtsov

Tlatova

Pevtsov

et al. 2019

A&A

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Context. Systematic observations of magnetic field strength and polarity in sunspots began at Mount Wilson Observatory (MWO), USA in early 1917. Except for a few brief interruptions, this historical dataset has continued until the present. Aims. Sunspot field strength and polarity observations are critical in our project of reconstructing the solar magnetic field over the last hundred years. We provide a detailed description of the newly digitized dataset of drawings of sunspot magnetic field observations. Methods. The digitization of MWO drawings is based on a software package that we developed. It includes a semiautomatic selection of solar limbs and other features of the drawing, and a manual entry of the time of observations, measured field strength, and other notes handwritten on each drawing. The data are preserved in an MySQL database. Results. We provide a brief history of the project and describe the results from digitizing this historical dataset. We also provide a summary of the final dataset and describe its known limitations. Finally, we compare the sunspot magnetic field measurements with those from other instruments, and demonstrate that, if needed, the dataset could be continued using modern observations such as, for example, the Vector Stokes Magnetograph on the Synoptic Optical Long-term Investigations of the Sun platform.

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“…A typical drawing (for a graphic example, see Figure 1 in Pevtsov and Clette, 2014) contains information about location of sunspot, its approximate size (penumbra and umbra) as well as polarity and maximum field strength of its magnetic field. The drawings were digitized (tabulated) using software package developed by us (e.g., Tlatova, Vasil'eva, and Pevtsov, 2015).The digitization included the date and time of observations, heliographic coordinates of each umbra, its area, the strength, and polarity of its magnetic field. The digitized dataset employed in this article contains 20318 days of observations, which cover period between January 1917 and October 2016.…”

Section: Datamentioning

confidence: 99%

Tilt of Sunspot Bipoles in Solar Cycles 15 to 24

et al. 2018

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We use recently digitized sunspot drawings from Mount Wilson Observatory to investigate the latitudinal dependence of tilt angles of active regions and its change with solar cycle. The drawings cover the period from 1917 to present and contain information about polarity and strength of magnetic field in sunspots. We identify clusters of sunspots of same polarity, and used these clusters to form "bipole pairs". The orientation of these bipole pairs was used to measure their tilts. We find that the latitudinal profile of tilts does not monotonically increase with latitude as most previous studies assumed, but instead, it shows a clear maximum at about 25-30 degree latitudes. Functional dependence of tilt (γ) on latitude (ϕ) was found to be γ = (0.20 ± 0.08) sin(2.80ϕ) + (−0.00 ± 0.06). We also find that latitudinal dependence of tilts varies from one solar cycle to another, but larger tilts do not seem to result in stronger solar cycles. Finally, we find the presence of a systematic offset in tilt of active regions (non-zero tilts at the equator), with odd cycles exhibiting negative offset and even cycles showing the positive offset.

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Long-term variations in the sunspot magnetic fields and bipole properties from 1918 to 2014

Cited by 12 publications

References 14 publications

The mean tilt of sunspot bipolar regions: theory, simulations and comparison with observations

The mean tilt of sunspot bipolar regions: theory, simulations and comparison with observations

Reconstructing solar magnetic fields from historical observations

Tilt of Sunspot Bipoles in Solar Cycles 15 to 24

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