Does the solar granulation change with the activity cycle?

Müller, R.; Hanslmeier, A.; Utz, D.; Ichimoto, Kiyoshi

doi:10.1051/0004-6361/201732085

Cited by 8 publications

(12 citation statements)

References 32 publications

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“…is dominated by the granulation variability, ν ∈ [ f , 2300] µHz, is not significantly affected by the solar magnetic cycle (see Seleznyov et al 2011;Muller et al 2018). Therefore, we can state that granulation variability is stationary with respect to the solar cycle (i.e., its statistical properties remain constant over the solar cycle).…”

Section: A Stationary Stochastic Colored Noisementioning

confidence: 94%

Mitigating flicker noise in high-precision photometry

Sulis

Lendl

Hofmeister

et al. 2020

A&A

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Context. In photometry, the short-timescale stellar variability (“flicker”), such as that caused by granulation and solar-like oscillations, can reach amplitudes comparable to the transit depth of Earth-sized planets and is correlated over the typical transit timescales. It can introduce systematic errors on the inferred planetary parameters when a small number of transits are observed. Aims. The objective of this paper is to characterize the statistical properties of the flicker noise and quantify its impact on the inferred transit parameters. Methods. We used the extensive solar observations obtained with SoHO/VIRGO to characterize flicker noise. We simulated realistic transits across the solar disk using SDO/HMI data and used these to obtain transit light curves, which we used to estimate the errors made on the transit parameters due to the presence of real solar noise. We make these light curves publicly available. To extend the study to a wider parameter range, we derived the properties of flicker noise using Kepler observations and studied their dependence on stellar parameters. Finally, we predicted the limiting stellar apparent magnitude for which the properties of the flicker noise can be extracted using high-precision CHEOPS and PLATO observations. Results. Stellar granulation is a stochastic colored noise, and is stationary with respect to the stellar magnetic cycle. Both the flicker correlation timescales and amplitudes increase with the stellar mass and radius. If these correlations are not taken into account when fitting for the parameters of transiting exoplanets, this can bias the inferred parameters. In particular, we find errors of up to 10% on the ratio between the planetary and stellar radius (Rp∕Rs) for an Earth-sized planet orbiting a Sun-like star. Conclusions. Flicker will significantly affect the inferred parameters of transits observed at high precision with CHEOPS and PLATO for F and G stars. Dedicated modeling strategies need to be developed to accurately characterize both the star and the transiting exoplanets.

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Section: A Stationary Stochastic Colored Noisementioning

confidence: 94%

Mitigating flicker noise in high-precision photometry

Sulis

Lendl

Hofmeister

et al. 2020

A&A

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“…We report, for the first time, a direct measurement of granule variations in the quiet Sun along the cycle; indirect clues of global modifications in granulation (integrated over the whole Sun) had already been suggested by variations in Fraunhofer line bisectors (e.g., Livingston 1982;Livingston et al 1999). Moreover, previous works indicated that variations in granulation during the cycle could be only of weak amplitude (Muller et al 2018); here we were able to sufficiently lower our detection level thanks in particular to the high stability and quality of the SDO/HMI instrument.…”

Section: Discussionmentioning

confidence: 60%

“…Nevertheless, we can observe the evolution of the dynamical properties of the granulation over a solar cycle. Thanks to Hinode observations, variations in intensity contrast and in granulation scales have been shown to be smaller than 3% (Muller et al 2018).…”

Section: Introductionmentioning

confidence: 97%

“…Satellites provide images without the terrestrial atmospheric distortions (seeing) and allow precise quantitative measurements of granule physical properties. Although the main characteristics of that granulation are widely described in the literature (e.g., see Hirzberger et al 2002;Nordlund et al 2009;Lagg et al 2014;Fischer et al 2017;Falco et al 2017), the studies of its variations over activity cycles are limited (see references in Roudier & Reardon 1998;Muller et al 2018). This is mostly due to the difficulty in acquiring homogeneous sets of granulation images without atmospheric distortions over a whole 11-year solar cycle.…”

Section: Introductionmentioning

confidence: 99%

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Changes in granulation scales over the solar cycle seen with SDO/HMI and Hinode/SOT

Ballot

Roudier

Malherbe

et al. 2021

A&A

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Context. The Sun is the only star where the superficial turbulent convection can be observed at very high spatial resolution. The Solar Dynamics Observatory (SDO) has continuously observed the full Sun from space with multi-wavelength filters since July 2010. In particular, the Helioseismic and Magnetic Imager (HMI) instrument takes high-cadence frames (45 s) of continuum intensity in which solar granulation is visible. Aims. We aimed to follow the evolution of the solar granules over an activity cycle and look for changes in their spatial properties. Methods. We investigated the density of granules and their mean area derived directly from the segmentation of deconvolved images from SDO/HMI. To perform the segmentation, we define granules as convex elements of images. Results. We measured an approximately 2% variation in the density and the mean area of granules over the cycle, the density of granules being greater at solar maximum with a smaller granule mean area. The maximum density appears to be delayed by about one year compared to classical activity indicators, such as the sunspot number. We complemented this study with high-spatial-resolution observations obtained with Hinode/SOTBFI (Solar Optical Telescope Broadband Filter Imager), which are consistent with our results. Conclusions. The observed variations in solar granulation at the disc centre reveal a direct insight into the change in the physical properties that occur in the upper convective zone during a solar cycle. These variations can be due to interactions between convection and magnetic fields, either at the global scale or, locally, at the granulation scale.

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“…Attempts of investigating variations in the convection patterns over the activity cycle are not numerous (see, in particular, references in Roudier & Reardon 1998;Muller et al 2018). Lefebvre et al (2008) found that the granulation evolves with height in the photosphere but does not exhibit considerable variations in the activity cycle.…”

Section: Introductionmentioning

confidence: 99%

Spatial Spectrum of Solar Convection from Helioseismic Data: Flow Scales and Time Variations

Гетлинг¹,

Kosovichev²

2022

Preprint

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We analyze spectral properties of solar convection in the range of depths from 0 to 19 Mm using subsurface flow maps obtained by the time-distance helioseismology analysis of solar-oscillation data from the Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamics Observatory (SDO) from May 2010 to September 2020. The results reveal a rapid increase of the horizontal flow scales with the depth, from supergranulation to giant-cell scales, and support the evidence of large-scale convection, previously detected by tracking the motion of supergranular cells on the surface. Furthermore, the total power of convective flows correlates with the solar activity cycle. During the solar maximum, the total power decreases in shallow subsurface layers and increases in the deeper layers.

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Does the solar granulation change with the activity cycle?

Cited by 8 publications

References 32 publications

Mitigating flicker noise in high-precision photometry

Mitigating flicker noise in high-precision photometry

Changes in granulation scales over the solar cycle seen with SDO/HMI and Hinode/SOT

Spatial Spectrum of Solar Convection from Helioseismic Data: Flow Scales and Time Variations

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