Spot activity cycles and flip‐flops on young solar analogs

Berdyugina, S. V.; Järvinen, S. P.

doi:10.1002/asna.200410390

Cited by 39 publications

(36 citation statements)

References 25 publications

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“…The solar active longitudes and their behaviour are very similar to stellar activity phenomena, including the flip-flop cycle detected in binaries and solar-type stars (Berdyugina & Tuominen 1998;Berdyugina 2004;Berdyugina & Järvinen 2005). On the Sun the flip-flop phenomenon is observed as the alternation of the major spot activity between the opposite longitudes with a 3.7 year cycle (BU03).…”

Section: Introductionmentioning

confidence: 66%

Preferred sunspot longitudes: non-axisymmetry and differential rotation

Usoskin¹,

Berdyugina²,

Poutanen³

2005

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Abstract.As recently found, the distribution of sunspots is non-axisymmetric and spot group formation implies the existence of two persistent active longitudes separated by 180• . Here we quantitatively study the non-axisymmetry of sunspot occurrence. In a dynamic reference frame inferred from the differential rotation law, the raw sunspot data show a clear clustering around the persistent active longitudes. The differential rotation describing the dynamic frame is quantified in terms of the equatorial angular velocity and the differential rotation rate, which appear to be significantly different from those for individual sunspots. This implies that the active longitudes are not linked to the depth of sunspot anchoring. In order to quantify the observed effect, we introduce a measure of the non-axisymmetry of the sunspot distribution. The non-axisymmetric component is found to be highly significant, and the ratio of its strength to that of the axisymmetric one is roughly 1:10. This provides additional constraints for solar dynamo models.

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Section: Introductionmentioning

confidence: 66%

Preferred sunspot longitudes: non-axisymmetry and differential rotation

Usoskin¹,

Berdyugina²,

Poutanen³

2005

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“…We know that a shorter period usually refers to faster rotation due to tidal interaction (Walter & Bowyer 1981), and thus implies magnetic activity (Noyes et al 1984). For instance, the RS CVn variables on which flares are observed are short period detached binaries with strong magnetic activity (Berdyugina & Järvinen 2005). Figure 8(a) is the AL ave variation along P orb , which is extracted from the KEB catalog.…”

Section: The Effect Of Orbital Period and Rotationmentioning

confidence: 99%

White-Light Flares on Close Binaries Observed With Kepler

Gao

Xin

Liu

et al. 2016

ApJS

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Based on Kepler data, we present the results of a search for white light flares on 1049 close binaries. We identify 234 flare binaries, of which 6818 flares are detected. We compare the flare-binary fraction in different binary morphologies ("detachedness"). The result shows that the fractions in over-contact and ellipsoidal binaries are approximately 10%-20% lower than those in detached and semi-detached systems. We calculate the binary flare activity level (AL) of all the flare binaries, and discuss its variations along the orbital period (P orb ) and rotation period (P rot , calculated for only detached binaries). We find that the AL increases with decreasing P orb or P rot , up to the critical values at P orb ∼ 3 days or P rot ∼ 1.5 days, and thereafter the AL starts decreasing no matter how fast the stars rotate. We examine the flaring rate as a function of orbital phase in two eclipsing binaries on which a large number of flares are detected. It appears that there is no correlation between flaring rate and orbital phase in these two binaries. In contrast, when we examine the function with 203 flares on 20 non-eclipse ellipsoidal binaries, bimodal distribution of amplitude-weighted flare numbers shows up at orbital phases 0.25 and 0.75. Such variation could be larger than what is expected from the cross section modification.

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“…In addition to the four suspected active longitudes undergoing latitudinal migration, there are strong indicators that the photospheric and chromospheric characteristics are closely related to the magnetic surface activity of a solar-type MS star. Active longitudes are common among cool, magnetically active stars, ranging in evolutionary stage from zero-MS stars (Berdyugina & Järvinen 2005) to solar-type stars (Berdyugina & Usoskin 2003;Lanza et al 2009) and rapidly rotating red giants (Berdyugina & Tuominen 1998;Korhonen et al 2002). Being attributed to a non-axisymmetric component of a largescale magnetic field Moss 2005), these longitudes normally coexist with an axisymmetric component responsible for overall cyclic variations in stellar activity.…”

Section: Possible Magnetic Field Generatorsmentioning

confidence: 99%

First detection of a weak magnetic field on the giant Arcturus: remnants of a solar dynamo?

Sennhauser

Berdyugina

2011

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Context. Arcturus is the second closest K giant and among the brightest stars in the sky. It has not been found to have a magnetic field, even though Ca ii H&K lines as activity indicators imply that Arcturus is magnetically active. Aims. We measure the mean longitudinal magnetic field strengths and interpret them in terms of an intraseasonal activity modulation. Methods. We apply our new Zeeman component decomposition (ZCD) technique to three single sets of Stokes I and V spectra to measure the longitudinal component of the magnetic field responsible for tiny Zeeman signatures detected in spectral line profiles. Results. For two of the spectra, we report the detection of the Zeeman signature of a weak longitudinal magnetic field of 0.65 ± 0.26 G and 0.43 ± 0.16 G. The third measurement is less significant, but all the measurements closely reproduce a rotationally modulated activity cycle with four active longitudes. Conclusions. For the first time, a magnetic field on Arcturus is directly detected. This field can be attributed to a diminishing solartype αΩ-dynamo acting in the deepening convection zone of Arcturus. We demonstrate that our new method ZCD lowers the detection limit of very weak magnetic fields from spectropolarimetric measurements.

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Spot activity cycles and flip‐flops on young solar analogs

Cited by 39 publications

References 25 publications

Preferred sunspot longitudes: non-axisymmetry and differential rotation

Preferred sunspot longitudes: non-axisymmetry and differential rotation

White-Light Flares on Close Binaries Observed With Kepler

First detection of a weak magnetic field on the giant Arcturus: remnants of a solar dynamo?

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