The Properties of the Tilts of Bipolar Solar Regions

Illarionov, Egor; Tlatov, A. G.; Sokoloff, D.

doi:10.1007/s11207-014-0612-9

Cited by 17 publications

(15 citation statements)

References 15 publications

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“…One can see that strong ARs, in general, obey Joy's law and have tilt of about ten degrees while weaker ARs exhibit scatter of tilt in a wide range of angles. The similar results were obtained by Illarionov, Tlatov, and Sokoloff (2015) who analysed distribution of tilt angles for large and small magnetic dipoles (see fig. 1 in Illarionov, Tlatov, and Sokoloff 2015).…”

Section: Resultssupporting

confidence: 86%

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Extended statistical analysis of emerging solar active regions

Kutsenko

Abramenko

Pevtsov

2019

Monthly Notices of the Royal Astronomical Society

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We use observations of line-of-sight magnetograms from Helioseismic and Magnetic Imager (HMI) on board of Solar Dynamics Observatory (SDO) to investigate polarity separation, magnetic flux, flux emergence rate, twist and tilt of solar emerging active regions. Functional dependence of polarity separation and maximum magnetic flux of an active region is in agreement with a simple model of flux emergence as the result of buoyancy forces. Our investigation did not reveal any strong dependence of emergence rate on twist properties of active regions.

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Section: Resultssupporting

confidence: 86%

“…The similar results were obtained by Illarionov, Tlatov, and Sokoloff (2015) who analysed distribution of tilt angles for large and small magnetic dipoles (see fig. 1 in Illarionov, Tlatov, and Sokoloff 2015). Although tilt of an AR varies during the emergence phase (e.g.…”

Section: Resultssupporting

confidence: 86%

Extended statistical analysis of emerging solar active regions

Kutsenko

Abramenko

Pevtsov

2019

Monthly Notices of the Royal Astronomical Society

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“…This translates to roughly 100 MSH total group area. For this lower limit of group areas, Illarionov et al (2015) give an anti-Hale fraction of about 37%, while for large groups with 500 MSH or more, that fraction is 10% or less. The unsigned tilt angle distribution of anti-Hale groups is broader than that of the Hale groups, but with similar peaks (McClintock et al 2014).…”

Section: Sources Of Errorsmentioning

confidence: 86%

“…The anti-Hale fraction of all groups is about 8% (Li & Ulrich 2012;McClintock et al 2014) or about 5% (Sokoloff & Khlystova 2010) or even lower , based on magnetogram data. This fraction holds true for large bipolar regions though, while the fraction may be as high as 50% for ephemeral regions with areas less than 50 MSH (Illarionov et al 2015), which are not relevant here as they are not accompanied by sunspots. In our cleanest Fig.…”

Section: Sources Of Errorsmentioning

confidence: 93%

Sunspot areas and tilt angles for solar cycles 7–10

Pavai

Arlt

Dasi-Espuig

et al. 2015

A&A

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Aims. Extending the knowledge about the properties of solar cycles into the past is essential for understanding the solar dynamo. This paper aims to estimate areas of sunspots observed by Schwabe in 1825−1867 and to calculate the tilt angles of sunspot groups. Methods. The sunspot sizes in Schwabe's drawings are not to scale and need to be converted into physical sunspot areas. We employed a statistical approach assuming that the area distribution of sunspots was the same in the 19th century as it was in the 20th century. Results. Umbral areas for about 130 000 sunspots observed by Schwabe were obtained, as well as the tilt angles of sunspot groups assuming them to be bipolar. There is, of course, no polarity information in the observations. The annually averaged sunspot areas correlate reasonably with sunspot number. We derived an average tilt angle by attempting to exclude unipolar groups with a minimum separation of the two alleged polarities and an outlier rejection method which follows the evolution of each group and detects the moment it turns unipolar at its decay. As a result, the tilt angles, although displaying considerable scatter, average to 5.• 85 ± 0.• 25, with the leading polarity located closer to the equator, in good agreement with tilt angles obtained from 20th century data sets. Sources of uncertainties in the tilt angle determination are discussed and need to be addressed whenever different data sets are combined. The sunspot area and tilt angle data are provided at the CDS.

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“…Tilt angle scatter about Joy's law introduced by convection increases as flux decreases in thin flux tube models by Weber et al (2013). Illarionov et al (2015) showed the significant scatter in bipolar regions with areas less than 300 MSH (including ephemeral regions without sunspot activity). A transition occurs between 300 and 400 MSH where the distribution of larger regions becomes dominated by sunspot activity with substantially less tilt angle scatter and more tilt angles that follow Joy's law.…”

Section: Introductionmentioning

confidence: 98%

Tilt Angle and Footpoint Separation of Small and Large Bipolar Sunspot Regions Observed With Hmi

McClintock

Norton

2016

ApJ

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We investigate bipolar sunspot regions and how tilt angle and footpoint separation vary during emergence and decay. The Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory collects data at a higher cadence than historical records and allows for a detailed analysis of regions over their lifetimes. We sample the umbral tilt angle, footpoint separation, and umbral area of 235 bipolar sunspot regions in Helioseismic and Magnetic Imager -Debrecen Data (HMIDD) with an hourly cadence. We use the time when the umbral area peaks as time zero to distinguish between the emergence and decay periods of each region and we limit our analysis of tilt and separation behavior over time to within ±96 hours of time zero. Tilt angle evolution is distinctly different for regions with small (≈ 30 MSH), midsize (≈ 50 MSH), and large (≈ 110 MSH) maximum umbral areas, with 45 and 90 MSH being useful divisions in separating the groups. At the peak umbral area, we determine median tilt angles for small (7.6 • ), midsize (5.9 • ) and large (9.3 • ) regions. Within ±48 hours of the time of peak umbral area, large regions steadily increase in tilt angle, midsize regions are nearly constant, and small regions show evidence of negative tilt during emergence. A period of growth in footpoint separation occurs over a 72-hr period for al of thel regions from roughly 40 to 70 Mm. The smallest bipoles (< 9 MSH) are outliers in that they do not obey Joy's law and have a much smaller footpoint separation. We confirm Muñoz-Jaramillo et al. (2015) results that the sunspots appear to be two distinct populations.

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The Properties of the Tilts of Bipolar Solar Regions

Cited by 17 publications

References 15 publications

Extended statistical analysis of emerging solar active regions

Extended statistical analysis of emerging solar active regions

Sunspot areas and tilt angles for solar cycles 7–10

Tilt Angle and Footpoint Separation of Small and Large Bipolar Sunspot Regions Observed With Hmi

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