Supergiant Complexes of Solar Activity and Convection Zone

Arkhypov, O. V.; Antonov, O. V.; Khodachenko, M. L.

doi:10.1007/s11207-011-9734-5

Cited by 6 publications

(7 citation statements)

References 19 publications

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“…, which is similar to that used in our previous solar studies (Arkhypov et al 2011(Arkhypov et al , 2013. Figure 7 shows the values of τ 1 and τ 2 obtained with the old (Arkhypov et al 2015a) and current (modified) methods.…”

Section: Modified Methods For Harmonics' Timescale Measurementsupporting

confidence: 66%

“…It has been found that the large-scale pattern of solar activity shows the timescales of large longitudinal harmonics (with numbers m < 20), in agreement with Kolmogorov's theory of turbulence (Arkhypov et al 2011(Arkhypov et al , 2013. Moreover, turbulent cascades have now been identified in the power spectra of solar activity variations at scales up to 380 Mm, or at m  10 (Arkhypov et al 2013).…”

Section: Introductionsupporting

confidence: 69%

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Deep Mixing in Stellar Variability: Improved Method, Statistics, and Applications

Arkhypov

Khodachenko

Lämmer

et al. 2016

ApJ

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The preliminary results on deep-mixing manifestations in stellar variability are tested using our improved method and extended data set. We measure the timescales τ m of the stochastic change in the spectral power of rotational harmonics with numbers m 3 in the light curves of 1361 main-sequence stars from the Kepler mission archive. We find that the gradient t t --log log log 2 log 1 2 1has a histogram maximum at −2/3, demonstrating agreement with Kolmogorov's theory of turbulence and therefore confirming the manifestation of deep mixing. The squared amplitudes of the first and second rotational harmonics, corrected for integral photometry distortion, also show a quasi-Kolmogorov character with spectral index ≈−5/3. Moreover, the reduction of τ 1 and τ 2 to the timescales τ lam1 and τ lam2 of laminar convection in the deep stellar layers reveals the proximity of both τ lam1 and τ lam2 to the turnover time τ MLT of standard mixing length theory. Considering this result, we use the obtained stellar variability timescales instead of τ MLT in our analysis of the relation between stellar activity and the Rossby number P/τ MLT . Comparison of our diagrams with previous results and theoretical expectations shows that best-fit correspondence is achieved for τ lam1 , which can therefore be used as an analog of τ MLT . This means that the laminar component (giant cells) of stellar turbulent convection indeed plays an important role in the physics of stars. Additionally, we estimate the diffusivity of magnetic elements in stellar photospheres.

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Section: Modified Methods For Harmonics' Timescale Measurementsupporting

confidence: 66%

Section: Introductionsupporting

confidence: 69%

Deep Mixing in Stellar Variability: Improved Method, Statistics, and Applications

Arkhypov

Khodachenko

Lämmer

et al. 2016

ApJ

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“…Breaking up the light curve in chunks of one rotation period length and calculation of individual C The study of the longitudinal distribution of stellar activity helps to reveal photospheric manifestations of deep convection. These manifestations were found in the Sun (Arkhypov et al 2011(Arkhypov et al , 2013 and reproduced in numerical modeling (Weber et al 2013). 4.…”

Section: Satisfied Then We Replace the Measured F(t) With The Value mentioning

confidence: 71%

“…However, turbulent cascades have now been identified in the power spectra of variations of solar activity at scales up to 380 Mm (Arkhypov et al 2013). Moreover, the timescales of variability for activity complexes of global sizes (>190 Mm) were shown to be consistent with the predictions of Kolmogorov's theory of turbulence (Arkhypov et al 2011(Arkhypov et al , 2013. These features are the "fingerprints" of turbulence deep in the solar CZ.…”

Section: Introductionmentioning

confidence: 75%

“…(7) is the inverted time, and b m < 0, one can introduce the timescale τ m = −1/b m . In view of the fact that the manifestation of deep mixing was found in the linear term of the logarithmic approximation of the solar activity autocorrelation (Arkhypov et al 2011(Arkhypov et al , 2013), below we check whether the analogous stellar parameter τ m = −1/b m is related to τ MLT .…”

Section: Satisfied Then We Replace the Measured F(t) With The Value mentioning

confidence: 99%

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Signs of deep mixing in starspot variability

Arkhypov

Khodachenko

Güdel

et al. 2015

A&A

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The current knowledge on plasma mixing in stellar interiors is based on theoretical modeling, which calibrates the empirical relations between the mixing and observable stellar parameters. Hence, a model-independent method of studying the mixing process is a desirable, but yet unfounded approach. Here, using a new spectral-correlation method, verified for the Sun, we show that deep mixing is manifested in stellar photometric light curves. We measure the timescales of the stochastic change in the spectral power of rotational variability of hundreds of main-sequence stars from the Kepler mission archive. The discovered proportionality of these timescales to the turnover time of the standard mixing length theory, their consistency with Kolmogorov's theory of turbulence, and the relation with stellar activity provide a new approach to the probing of stellar interiors. This opens a broad perspective for experimental studies of deep mixing and magnetic dynamos in stars.

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