Filaments and the magnetic configuration. I. Observation of the solar case

Meunier, N.; Delfosse, X.

doi:10.1051/0004-6361/201116834

Cited by 5 publications

(2 citation statements)

References 27 publications

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“…Rust 1966;Kuperus & Tandberg-Hanssen 1967;Hirayama 1985;Mouradian 1998;Ulrich et al 2002). Meunier & Delfosse (2011) quantified this relationship based on a systematic comparison of filament positions and magnetograms. However, there are more PIL pixels during cycle minimum, and less during cycle maximum because of the presence of large unipolar areas, while there are far fewer filaments during cycle minimum.…”

Section: Filament Propertiesmentioning

confidence: 99%

Relationship between Ca and Hα chromospheric emission in F-G-K stars: Indication of stellar filaments?

Meunier¹,

Kretzschmar

Gravet

et al. 2022

A&A

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Context. Different relationships between the Hα and Ca II chromospheric emissions have been reported in solar-type stars. In particular, the time-series of emissions in these two lines are clearly anti-correlated for a few percent of the stars, contrary to what is observed on the Sun. Aims. Our objective is to characterise these relationships in more detail using complementary criteria, and to constrain the properties of filaments and plages that are necessary to explain the observations. Methods. We analysed the average level and variability of the Hα and Ca II emission for 441 F-G-K stars, paying particular attention to their (anti-)correlations on both short and long timescales. We also computed synthetic Hα and Ca II time-series for different assumptions of plage and filament properties and compared them with the observations. Results. We were not able to find plage properties that, alone, are sufficient to reproduce the observations at all timescales simultaneously, even when allowing different Hα and Ca II emission relationships for different stars. We also specified the complex and surprising relationship between the average activity levels of both indexes, in particular for low-activity stars. Conclusions. We conclude that plages alone are unlikely to explain the observed variety of relationships between Ca II and Hα emission, and that the presence of other phenomena like filaments may help to reconcile the models with observations.

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Section: Filament Propertiesmentioning

confidence: 99%

Relationship between Ca and Hα chromospheric emission in F-G-K stars: Indication of stellar filaments?

Meunier¹,

Kretzschmar

Gravet

et al. 2022

A&A

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“…Meunier et al 2010a,b, Lagrange et al 2010, Borgniet et al 2015, Marchwinski et al 2015. Meunier & Delfosse (2011) found that the correlation between the Hα and the CaII activity indices depends on the activity cycle.…”

Section: The Sun As a Starmentioning

confidence: 99%

Dealing with activity in RV planet searches

Boisse¹

2015

Proc. IAU

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Precise radial velocity measurements of a star allow to search for planets. But this method has to face with irregularly time series. Stellar variabilities: pulsation, granulation, stellar activity on a short and long timescale, also modify the measure of the radial velocities. There is indeed a growing literature of controversies on how a signal is interpreted as a planet or due to stellar activity. I present how the star variations change the measured RVs, which techniques and indices are used by several teams to disentangle activity and planets, and the future options that are being studied.

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