Flip‐flop phenomenon: observations and theory

Elstner, D.; Korhonen, H.

doi:10.1002/asna.200410389

Cited by 56 publications

(60 citation statements)

References 15 publications

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“…For that reason we synthesized from the α 2 Ω-dynamo simulation of Elstner & Korhonen (2005), 12 phase resolved spectra at phases which correspond to our observations. The dynamo model was scaled to have a peak field strength of 1920 G. The stellar parameter are those from V410 Tau given in Sect.…”

Section: Appendix B: Test Inversion With a Dynamo Modelmentioning

confidence: 86%

“…But a possible explanation can still be given in terms of an α 2 Ω-dynamo (Elstner & Korhonen 2005), where the non-axisymmetric solution is modulated by an oscillatory axisymmetric mode. The excitation of such an α 2 Ω-dynamo can already occur at a very low differential rotation rate (Elstner & Korhonen 2005). To qualitatively compare this dynamo model with our reconstructions we have taken a snapshot of the non-axisymmetric mode of these simulations at a time when both magnetic polarities are of approximately the same strength.…”

Section: The Magnetic Nature Of V410 Taumentioning

confidence: 99%

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The magnetic field topology of the weak-lined T Tauri star V410 Tauri

Carroll

Strassmeier

Rice

et al. 2012

A&A

114

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Aims. In a follow-up investigation we present Zeeman-Doppler maps of the weak-lined T Tauri star (WTTS) V410 Tau. As a rapid rotating star and a typical WTTS the stellar surface of V410 Tau is accessible to surface imaging techniques and allows us to detect and reconstruct the major magnetic surface features on this pre-main sequence star. Methods. The polarized signals we are measuring are on the order of 10 −4 to 10 −3 and are hidden well below the noise level of a single observation. A new line profile reconstruction technique based on a singular value decomposition (SVD) allows us to extract the weak polarized line profiles (Stokes V) as well as the intensity profiles (Stokes I). One of the key features of the line profile reconstruction is that the SVD line profiles are amenable to radiative transfer modeling within our Zeeman-Doppler Imaging code iMap. The code also utilizes a new iterative regularization scheme which is independent of any additional surface constraints. To provide more stability a vital part of our inversion strategy is to invert both Stokes I and Stokes V profiles to simultaneously reconstruct the temperature and magnetic field surface distribution of V410 Tau. A new image-shear analysis is also implemented to allow the search for image and line profile distortions induced by a differential rotation of the star. Results. The magnetic field structure we obtain for V410 Tau shows a good spatial correlation with the surface temperature and is dominated by a strong field within the cool polar spot. The Zeeman-Doppler maps exhibit a large-scale organization of both polarities around the polar cap in the form of a twisted bipolar structure. The magnetic field reaches a value of almost 2 kG within the polar region but smaller fields are also present down to lower latitudes. The pronounced non-axisymmetric field structure and the nondetection of a differential rotation for V410 Tau supports the idea of an underlying α 2 -type dynamo, which is predicted for WTTS.

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Section: Appendix B: Test Inversion With a Dynamo Modelmentioning

confidence: 86%

Section: The Magnetic Nature Of V410 Taumentioning

confidence: 99%

The magnetic field topology of the weak-lined T Tauri star V410 Tauri

Carroll

Strassmeier

Rice

et al. 2012

A&A

114

View full text Add to dashboard Cite

show abstract

“…The results from the thick and thin convection zone flip-flop models, that were first discussed in Elstner & Korhonen (2005), have been converted into light-curves as described in the previous section. The model parameters are given in Table 2.…”

Section: Resultsmentioning

confidence: 99%

Photometric observations from theoretical flip-flop models

Korhonen

Elstner

2005

A&A

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Abstract. Some active stars show a so-called flip-flop phenomenon in which the main spot activity periodically switches between two active longitudes that are 180 • apart. In this paper we study the flip-flop phenomenon by converting results from dynamo calculations into long-term synthetic photometric observations, which are then compared to the real stellar observations. We show that similar activity patterns as obtained from flip-flop dynamo calculations, can also be seen in the observations. The long-term light-curve behaviour seen in the synthesised data can be used for finding new stars exhibiting the flip-flop phenomenon.

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“…Bigazzi and Ruzmaikin (2003) explain the Suns preferred longitudes as a coupling of the magnetic dynamo modes. Elstner and Korhonen (2005) believe that, 'to explain 246 V. N. Obridko this phenomenon, a non-axisymmetric dynamo mode, giving rise to two permanent active longitudes at opposite stellar hemispheres, is needed together with an oscillating axisymmetric magnetic field'. Axel Brandenburg and Petri J. Käpylä (2005) solve a two-dimensional mean field dynamo model where magnetic helicity conservation is fully included.…”

Section: Active Longitudesmentioning

confidence: 99%

Large-scale patterns and ‘active longitudes’

Обридко¹

2009

Proc. IAU

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Abstract. The following aspects of the physics of large-scale solar magnetic fields are discussed: structure of large-scale fields (LSF) and connection with local fields; dynamo and origin of LSF; LSF cycle variation; meridional circulation and LSF; rotation of LSF; fine structure of the field in quiet regions and the concept of the pebble-shaped field; active longitudes, their manifestation in various solar indices, and dependence on the power of solar activity.

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Flip‐flop phenomenon: observations and theory

Cited by 56 publications

References 15 publications

The magnetic field topology of the weak-lined T Tauri star V410 Tauri

The magnetic field topology of the weak-lined T Tauri star V410 Tauri

Photometric observations from theoretical flip-flop models

Large-scale patterns and ‘active longitudes’

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